Testing weather lore in school

Transcription

Freeland
Testing weather lore in
school
Peter Freeland
Rhymes and sayings used to predict weather conditions were once
relied on by farmers, but how accurate are they?
Throughout the 19th century and during the first
quarter of the 20th century, agricultural workers in
the UK built up a collection of rhymes and sayings
that were used to predict weather conditions. This,
of course, was in the days before accurate weather
forecasts were broadcast over the radio or became
a regular feature of television. The form in which
agricultural workers learned their weather lore
depended very much on two factors:
l Geographic location. Although the message
conveyed by each rhyme or saying might be the
same across the country, the choice of words
was variable, differing from county to county
and even, in some cases, from village to village.
Most of the weather lore listed below is in the
form that I learned it from my grandparents and
uncles, who either owned farms or worked as
agricultural labourers in East Sussex.
l Rhyme or saying. Rhyming forms were generally preferred, probably because they are easier
to remember.
Some schools have kept weather records for more than
100 years. Today, when simple recording devices are
available from suppliers, it is common for pupils to
record maximum and minimum daily temperatures,
ABSTRACT
Many schools keep fairly detailed daily records
of weather conditions. This is an area of science
in which some pupils are particularly interested.
Before the advent of weather forecasts, farmers
and gardeners relied on weather lore for
clues, both short-term and long-term, about
approaching weather systems. These rhymes
and sayings were often stated in the form of
a hypothesis, capable of being tested. In this
article more than 40 such rhymes or sayings are
listed, with suggestions about ways in which
most can be evaluated. The activities would be
appropriate for 9–12 year-olds.
daily rainfall, air pressure, wind velocity, hours of
sunshine, cloud types, and so on. A great deal can be
learned by processing these data in ways that extract
maximum information. Studying the weather in this
way provides a very good introduction to scientific
method. The aim of this article is to broaden that
study by introducing weather-related hypotheses
that can be tested with recorded data. Pupils should
be encouraged to decide for themselves whether the
main point of each rhyme or saying is (a) true, (b)
probable, (c) unlikely or (d) false. During this work
several opportunities are presented for introducing
the concept of probability. The sayings are presented
under four topic headings, with notes to explain how
they were applied and, in most cases, how they can
be tested. The activities would be appropriate for
9–12 year-olds.
Clouds, rain, snow, ice and vapours
In order to make maximum use of the items listed in
this section, pupils need to be able to recognise the
five cloud types illustrated in Figure 1 and described
in Table 1. They should know the difference between
a high-pressure system, or anticyclone, and a lowpressure system, also called a cyclone or depression.
When a depression approaches, its leading edge is
associated with a warm front, whereas its trailing
edge carries a cold one. They should also appreciate
that the movement of weather systems across the UK
is predominantly from west to east.
1 The higher the clouds, the fairer the weather.
The two highest types of cloud, cirrus (Figure 2) and
cirrostratus, are not rain-bearing clouds, although
cirrostratus often forms as a depression approaches
(see 13). Cirrocumulus is frequently associated with
showery weather (see 3), while both nimbostratus
and cumulonimbus, generally developed at lower
levels, bring rain.
Does it ever rain on days when cirrus clouds are
the only ones present at 9.0 a.m.?
School Science Review, September 2006, 88(322)
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Testing weather lore in school cirrostratus
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cumulonimbus
cirrus
cirrocumulus
nimbostratus
Figure 1 Cloud types.
2 The more cloud types at dawn, the greater the
chance of rain.
This saying could only be applied in summer, when
cumulonimbus clouds were present. The combination
of these clouds with other types, especially cirrus,
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was taken as a sign that thunderstorms were likely
later in the day.
On how many days of the year are cumulonimbus
clouds present at 9.0 a.m.? Do they occur in
combination with other cloud types and, if so, can
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Table 1 Common names and features of cloud types.
Cloud
Common name Features
Cirrus
‘feathery’ or ‘wispy’ clouds discrete white, transparent high clouds, formed from long strands of ice crystals
Cirrostratus
‘halo’ clouds
grey-white sheets of transparent high cloud, formed from ice crystals and thickening as a warm front approaches
Cirrocumulus ‘mackerel sky’
groups of discrete grey-white blocks of high cloud, with spaces between one block and the next
Nimbostratus rain clouds
grey, low, fast-moving clouds accompanied by light to moderate precipitation of rain or snow
Cumulonimbus thunder clouds
massive, towering and rolling clouds, white at the top and grey-black at the lowest level, accompanied by heavy precipitation of rain or hail, lightning and thunder
Figure 2 High, feather-like cirrus clouds on a summer’s afternoon.
the rainfall on that day be related to the number of
cloud types present in the early morning?
3 Mackerel sky, mackerel sky,
never long wet, never long dry.
A mackerel sky is one where cirrocumulus clouds,
associated with showery weather, occur.
Is the weather always showery when this type
of cloud is present? If so, measure and record the
duration of wet and dry periods throughout the day.
4 Rain before seven, fine before eleven.
This saying, of course, applies to the morning, not
the evening. Air temperatures are generally lower
at 7.0 a.m. than they are at 11.0 a.m. Water vapour
tends to become supersaturated and fall as rain if
temperatures fall. The reverse process, evaporation,
occurs as temperatures rise, which explains why
rainfall is less likely at 11.0 a.m. than it is at 7.0
a.m.
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Testing weather lore in school Freeland
On how many days of the year does this saying
apply? Does it apply more in the summer than in the
winter? If so, how do you explain the difference?
If you live within 5 miles of a railway station,
or 20 miles of an airport, record the days on which
you can hear train noise, or aircraft taking off, and
attempt to relate your findings to weather conditions
on those days.
5 The farther the sight, the nearer the rain.
Put in a different way, this saying means that if a
rain-bearing depression is approaching, you get a
clearer, more distinct view of distant objects, such as
trees or buildings on hills. This effect may, in part, be
due to a rise in humidity, which settles dust, and an
increase in wind velocity, which disperses smoke or
haze. Distant objects viewed through moisture-laden
air may also be slightly magnified.
If you live in a location where the visibility of a
distant object varies from day to day, record your
observations and attempt to relate them to prevailing
weather conditions.
6 Hear the whistle of a train?
’Tis a sign it’s going to rain.
This saying, dating from the early 20th century,
applied only on farms where train whistles would
not normally be audible (Figure 3). If one was heard,
it would be interpreted as advanced warning of
heavy, prolonged precipitation. Low, thick clouds,
which restrict the dissipation of sound, combined
with an increase in wind velocity, may account for
the effect.
7 Sun sets Friday, clear as bell:
rain on Monday, sure as hell.
Record the number of days on which there is a
clear sunset, without the sun being obscured by any
clouds. On how many occasions during a year does
rain fall three days later?
8 An icy wind from the north-east:
snow will fall on man and beast.
In S.E. England the predominant direction of snowbearing clouds in winter is from the north-east.
Moisture picked up over the North Sea is deposited,
as snow, mainly along the east coast.
Does a north-east wind, combined with sub-zero
temperatures, always result in a fall of snow? Does
this saying apply to all parts of the UK, or more to
some parts than others?
9 If there’s ice in November to hold up a duck,
for the rest of the year there’ll be slush and
muck.
In some forms of this ancient rhyme, possibly dating
from the 18th century, October, not November,
Figure 3 Under exceptionally thick cloud cover the sound of a steam train’s whistle may travel well beyond
its normal range.
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is mentioned. Following a succession of warm
autumns in S.E. England, there have been few, if
any, opportunities to test its validity.
12 If smoke goes up, the day is clear.
If smoke goes down, then rain is near.
The reference in this rhyme is to chimney smoke,
observed at dawn. In anticyclones, where winds are
light or absent, heat from fires causes dry smoke
to rise vertically. As a cyclone approaches, relative
humidity rises and wind velocity increases. Smoke
particles absorb water from moisture-laden air,
becoming heavier and more difficult to disperse.
Wind causes these particles to spread laterally, and
often downwards, into an area closer to the ground.
If you live in an area where coal fires are permitted, or are able to observe smoke from bonfires,
try to relate the direction of smoke dispersal to
weather conditions.
See also 13, 14, 15, 16, 17, 19, 21, 24, and 35.
10 When the dew is on the grass,
rain will never come to pass.
When grass is dry at morning light,
look for rain before the night.
Dew, formed as water vapour in the air cools and is
deposited as droplets on the surface of vegetation,
is most commonly seen on lawns and short-cropped
meadows during August and September. However,
it can form at any time of the year, including the
winter, when it often appears in the early morning
as white, reflective ice crystals, or frost. Both dew
and frost formations depend on air cooling rapidly,
which occurs mainly on clear, cloud-free nights,
within anticyclones. These, typically, are associated
with periods of dry, sunny weather, with little or no
cloud cover.
This saying is one of the more interesting because
it appears to have a high degree of probability. Keep
records throughout the year, and analyse them, in an
attempt to determine probability.
11 Morning fogs in May and September are
followed by warm, sunny afternoons.
Morning fogs in November–February are
followed by cold, overcast afternoons (or the
fog persists throughout the day).
Fog is a layer of low cloud extending to ground
level. The altitude of a fog depends primarily on air
temperature. Fogs tend to lift as temperatures rise,
but re-form when temperatures fall again, generally
after the sun has set. In May and September there
is sufficient heat associated with the sun’s rays to
cause the fog to lift as the morning progresses. By
the afternoon, when air temperatures are at their
highest, the fog may have completely dispersed,
leaving a cloud-free sky. However, in winter fogs
tend to persist because temperatures are generally
much lower and there is a much smaller difference
between morning and afternoon temperatures.
This occurs because winter sunlight rarely carries
sufficient heat to lift or disperse a fog.
Keep a record of days on which there is a morning
fog. Record also the temperatures on those days at
9.0 a.m., 12 noon and 3.0 p.m., and whether or not
the fog persists.
Attempt to relate the presence or absence of fog
to air temperature.
The sun and moon
When the sun is viewed through clouds, a fraction
of sunlight is absorbed while a different fraction is
transmitted. As a result of this, sunlit clouds may
appear white or orange-red when viewed at ground
level. The sun itself may be occluded by cloud
or appear to be surrounded by a halo, if its light
is transmitted through thin sheets of high cloud,
composed of ice crystals. The moon, reflecting light
from the sun, appears to pass through four phases:
new moon, first quarter, full moon and third quarter.
It, too, may be occluded by cloud or appear to be
surrounded by a halo.
13 A ring around the sun and moon:
a rainy day is coming soon.
A halo may form around the sun and moon when
they are partly occluded by continuous sheets of
high, thin clouds, composed of ice crystals. These
sheets of ice crystals, called cirrostratus at high
levels and altostratus at middle levels, increase in
number and thickness as a depression approaches.
The aura or halo that appears to surround the sun
or moon results from the reflection and scattering
of light. Typically, this effect is observed ahead of
storms with continuous precipitation.
Do haloes around the sun and moon get bigger
or smaller as the rain approaches? Can you think
of a possible explanation? What is the average time
interval between first observing a halo around the
sun and the precipitation of water vapour in the form
of rain or snow?
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14 Red sky at night, shepherds’ delight.
Red sky in the morning, shepherds’ warning.
This is one of the most widely known and used
rhymes for predicting weather conditions over the
next 12–48 hours. Sailors, not shepherds, feature
in some versions. A red sky in the morning is
probably caused by ice particles in high cirrus clouds
absorbing sunlight, leaving the longest wavelength,
red, to illuminate the morning sky (Figure 4). These
cirrus clouds develop in advance of rain-bearing
depressions. A red sky at night may be formed as
a result of a rise in air pressure that follows the
passage of a cold front. High pressure usually means
fine weather. A rapid rise in air pressure often causes
a thermal inversion, with a layer of warm air from
ground level rising above a layer of colder air. As this
warm air rises it carries dust particles and pollutants
to a great height, where they also act like ice
particles, transmitting red light (Figure 5). Another
well-known rhyme (15) makes similar points.
Is the popularity of rhymes 14 and 15 borne
out by their ability to predict weather conditions
accurately? Is rhyme 14 more accurate in its prediction of today’s weather than rhyme 15 is in
predicting tomorrow’s conditions?
15 Evening red and morning grey,
two sure signs of one fine day.
Evening grey and morning red,
a fall of rain will wet your head.
‘Grey’ in this rhyme probably refers more to fog,
mist and low cloud than to grey cloud at higher
altitudes.
Figure 4 Red sky in the morning, shepherds’ warning.
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16 A rainbow in the afternoon:
fair weather will be coming soon.
A rainbow forms when sunlight is diffracted into its
component wavelengths as it passes through falling
rain. Rainbows always occur in the part of the sky
opposite the sun; that is, in the western sky during
the morning and eastern sky during the afternoon.
Equipped with this information, farmers could
predict whether it was going to be wet or dry. The
trailing edge of a depression, where continuous
cloud cover is being replaced by patchy cloud, with
clear areas for sunlight penetration, provides suitable
conditions for rainbow formation. ‘Fair weather’ in
this rhyme refers to dry, sunny conditions that often
follow as a depression moves away. In the UK most
storms approach from the west. A rainbow in the
western sky is a sign of rain. A rainbow in the eastern
sky, which would occur in the afternoon or evening,
is a sign the rain has passed.
From your daily records of rainfall, compare the
amount of rain that fell in the week before a rainbow
appeared with that in the week that followed. How
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do your results compare for rainbows that appear
(a) in the morning and (b) in the afternoon?
behaviour provided useful hints about the weather
in the months ahead. While changes in animal
behaviour provided good short-term forecasts of
weather conditions, it was to plants he turned when
seeking longer-term predictions.
17 The moon upon its back,
holds water in its lap.
A crescent ‘new’ moon, positioned so that it
resembles a cup, with its base pointing towards the
earth, is the subject of this saying. Dry weather was
believed to accompany this phenomenon. However,
when the moon appears to change its position, to
become more vertical, downpours of torrential rain
can be expected as the moon empties its lap.
Again, from your daily records of rainfall, is
there any evidence to support this contention?
See also 7 and 41.
Animals and plants
18 Cats leap about and chase their tails,
to warn of thunderstorms and gales.
Cats, kept on farms to control mice and rats, were
watched closely in the belief that their behaviour
could be used to predict the approach of severe
storms (Figure 6). Behavioural changes taken as
indicators included increased restlessness and
playfulness, springing on moving objects, throwing
mice or inanimate objects into the air, climbing trees
and chasing their own tails. Cats also feature in
another rhyme:
The approach of a low-pressure system is marked
by a fall in air pressure, a rise in both temperature
and relative humidity, as well as an increase in
wind velocity. These changes, possibly acting in
combination, appear to affect the behaviour of
some animals, especially those kept on farms.
The continuous barking of dogs and the braying
of donkeys at dawn were said by my grandfather
to indicate the approach of rain. The old man also
observed animals living in the wild, believing their
One possible explanation of this behaviour is that dry
weather increases static electricity within the cat’s
fur. In order to stop the mild irritation this causes, the
cat moistens its fur more frequently, especially that
on its face and the top of its head.
If you own a cat or dog watch the TV for forecasts
of strong gales and thunderstorms. What behavioural
changes, if any, do you notice in your pet as the
If a cat washes its face o’er its ear,
’tis a sign the weather will be fine and clear.
Figure 5 Red sky at night, shepherds’ delight.
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Carry out your own investigations to determine
whether this saying is true or false. Would you rate
the probability of it being true as high or low?
What advantages might sheep and cattle gain from
huddling together during rain?
20 An early cuckoo heralds a fine summer.
St George’s Day, 23 April, served as a reference
point for interpreting this saying. It was going to
be a good summer if you heard the cuckoo before
that date. The early arrival of other migratory birds,
such as swallows and martins, was also interpreted
as a favourable omen, which promised dry, warm
conditions throughout their nesting seasons in late
April, May and June. Non-migratory, solitary species
such as thrushes, wood pigeons and crows were
observed during their nesting season to discover
whether they were building their nests high or low.
The higher they built, the greater the probability that
the summer would be warm and dry. If swallows and
martins, in groups of ten or more, were flying high,
repeatedly making circular flights, they were said to
be ‘wheeling’ or ‘drawing water from the well’, a
sign that rain was on the way.
On what date did you first hear the cuckoo?
What, if anything, did this indicate about mean
temperatures in May and June, an important time
for haymaking on farms?
Figure 6 Cats are said to become more alert and
active as a storm approaches.
storm approaches? Do you think such behaviour has
any biological or evolutionary significance?
19 Cows, all lying down together, are a sign of rain.
The operative word is ‘together’ and you need to
find a field where there are at least six or more cows
grazing. Ignore a situation in which some cows are
standing while others are lying down. It is only when
all the cows are huddled together, perhaps in one
corner of a field, and all lying down, that rain can
be expected.
A similar rhyme applies to sheep:
When sheep gather in a huddle,
tomorrow we shall have a puddle.
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21 Seagull, seagull, stay on the sand;
it’s never fair weather if you’re over land.
In calm weather seagulls obtain their food from the
sea and shoreline. However, gale-force winds, which
often prevent them from feeding in this way, drive
the birds inland to look for alternative food sources.
If you live near the coast, and have a clear
view of a roof or chimney stack where gulls perch
regularly, make daily counts of the number of birds
present at, say, 8.0 a.m. each day. Attempt to relate
numbers to weather conditions, especially wind
velocity. If you live further inland, record those days
on which seagulls were sighted. What was the wind
speed on those days? Do you think the gulls moved
inland before the storm arrived or as a result of it?
22 Birds fly high in a summer sky.
This saying applies primarily to flocks of birds, such
as ducks and rooks, that undertake daily migratory
flights over relatively short distances. The higher
they fly the more settled the weather. Wind speed
appears to be the critical factor. Unfortunately, there
is no simple way of testing the validity of this saying
except by observation.
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23 When leaves show you their undersides,
be very sure that rain betides.
The main reference in this old saying is to tall
hedges, planted with large-leaved species such
as hazel, beech and willows, rather than to trees.
Hedges thick enough to act as wind barriers generate
upward air currents on their windward side. This lifts
leaves from a horizontal position to one that is much
more vertical. As a result the lower side of leaves is
exposed to view. Winds of around 20–30 m.p.h., in
the outer bands of deep depressions with moderateheavy precipitation, are generally strong enough to
produce this effect.
Try to determine the velocity of wind required
to raise a 30–50 cm twig of hazel or similar plant
from a horizontal to a vertical position, using either
your own records or obtaining wind speeds from TV
weather forecasts. Does wind of this strength, in dry
conditions, provide a reliable indication that rain
will soon follow?
26 Onion skins very thin:
mild winter coming in.
Onion skins thick and tough:
coming winter cold and rough.
The skins of onions consist of dead, dry, parchmentlike leaf bases on the outside of more succulent ones.
It wasn’t only the texture of these skins that counted,
but also their number. Finding three or more layers of
skin, on a large onion lifted in August or September,
was an unfavourable sign.
Try to find out if the number of skins on onions is
a variable factor. Does it vary according to the size of
the bulb? Are there annual variations in the number
of skins on bulbs of approximately the same size? If
so, can this be related to (a) mean temperatures or
(b) total snowfall during the following winter?
See also 34, 40 and 41.
24 If the ash before the oak,
we shall surely get a soak.
If the oak before the ash,
we shall only get a splash.
This rhyme refers to bud-break in the terminal buds
of two common trees. One problem with it, which
may apply only in S.E. England, is that bud-break in
oak almost always occurs at least a fortnight before
that in ash, regardless of weather conditions.
In order to find out if the saying has validity
where you live, examine oak and ash twigs during
the last week of April and first week of May. Relate
your findings to total rainfall during May, June and
July.
25 A heavy harvest of nuts and berries before a
hard winter.
This was a fairly common belief among agricultural
workers who supposed that nature, in its providence,
compensated for the hardships of a cold winter by
providing an abundance of food for wildlife.
It is suggested that the ‘hardness’ of a winter
can be determined by measuring total snowfall, or
by calculating mean monthly midday temperatures
from November–March. Quadrats, placed beneath
trees such as oak, beech, sweet chestnut or horse
chestnut, can be used for a rough comparison of
seed production from year to year. Alternatively, ten
20 cm lengths of stems with berries, such as holly,
can be cut from plants and the average number of
fruits per stem determined.
Do you think this saying tells us more about the
conditions when these plants were pollinated than it
does about the coming winter?
Important dates in the farm calendar
Farm calendars in the 19th and early 20th centuries
owed much to the Church calendar, which specified
saints’ days, high days and holidays. Other influences
included the winter (21 December) and summer (21
June) solstices, the spring (21 March) and autumn
(21 September) equinoxes, and various phases of the
moon.
27 13 January (St Hilary’s Day)
As the days lengthen,
so doth the cold strengthen.
St Hilary’s Day was considered to coincide with the
coldest day of the year.
From your records do you find that (a) 13 January
was the coldest day of the year or (b) the coldest
day occurred between 21 December (shortest day)
and 13 January, with up to a week of increasing cold
between those dates?
28 2 February (Candlemas)
If Candlemas Day dawns bright and clear,
there’ll be two winters in the year.
There was a widespread belief amongst early
Christians in Europe that Candlemas Day, midway
between the winter solstice and spring equinox,
gave indications about the length of the winter. The
behaviour of hibernating animals such as hedgehogs
and badgers was observed, especially during the first
week of February. In 1880 a group of immigrants
in Pennsylvania, USA, began keeping an eye on
the groundhog, or woodchuck (Marmota monax), a
large rodent that hibernates in burrows. Legend has
it that if on the morning of 2 February, known today
throughout the USA as ‘Groundhog Day’, the animal
can see its shadow, there will be six more weeks of
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winter. If it cannot see its shadow, spring is on the
way. Regarded as one of the most important days in
the farm year, it was believed that the weather on 2
February gave insights into the conditions likely to
dominate the period of spring sowing.
Determine if there is sufficient sunlight on the
morning of 2 February to cast a shadow. Relate your
findings to mean monthly temperatures at midday
throughout February, March and April.
The saying can be tested by sowing 25 pea seeds
in pots or in a garden plot during April. Keep them
watered and weeded. How many pea plants do you
have when the pods are ripe? Were your losses
greater or smaller than 33 per cent?
29 1–7 and 25–31 March
If March comes in like a lion
it will go out like a lamb.
If March comes in like a lamb,
it will go out like a lion.
March is one of the windiest months of the year, often
with a rapid turnover of cyclones and anticyclones. It
may be that the last week of the month, when spring
sowing was underway, was of more importance
to farmers than the first week. Hence, the primary
purpose of the saying is to gain some foreknowledge
of the optimum time for sowing, leaving it in the last
week of the month if indications were favourable, or
doing it before or after that week if they weren’t.
The saying can be tested by keeping records
of wind speeds, preferably over several years, and
determining whether the predictions are borne out.
30 21 March (spring equinox)
The spring equinox coincides with one of the earliest
times for planting seeds and young plants out of
doors. However, it was considered foolhardy to plant
frost-tender plants, such as tomatoes or cucumbers,
or to sow the seeds of runner beans or marrows
before this date, or you might lose them as a result
of frost damage.
In the area where you live, what is the latest date
on which a frost was recorded? Use a maximum–
minimum thermometer to determine when the
temperature falls below 0 °C at night.
31 1–7 April
Sow one for me, one for thee and one for the crow.
Providing the weather was favourable, the first week
of April was considered the best time for sowing the
seeds of food crops grown in the vegetable garden.
Before the introduction of plant protection products,
some crops were ruined by poor weather conditions,
pests and diseases. Pea seeds, for instance, were
often eaten by mice, pigeons and magpies or rotted
by fungi. This saying recommends that you calculate
the number of plants you need and then sow onethird more in order to compensate for losses.
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32 23 April (St George’s Day)
See 20.
33 30 April to 20 May
Cast not a clout,’ till may be out.
’Till April’s dead, change not a thread.
This saying dates from a time when a single set of
clothing was worn throughout the winter. A ‘clout’
is a layer of old or well-worn clothing, and ‘may’
is not the month, but the white flowers of hawthorn
(Crataegus monogyna), generally in full bloom by
mid-May. The saying makes two claims. Firstly, it
warns that there are some days before the middle
of May when you might still need extra clothing.
Secondly, it implies that midday temperatures of
18 °C, or more – when you might wish to shed your
vest or shirt – are unlikely to be experienced for
more than a day or two until the may flowers are in
full bloom.
From your daily readings of midday temperatures
throughout May, and your observations of may
flowers in bloom, evaluate the validity of this
saying.
34 21 June (summer solstice)
The first harvests of new potatoes and peas were
made on or after this date. Digging potatoes,
or picking peas, before 21 June was considered
wasteful, because neither had been given sufficient
time to swell to a size that was suitable for serving
at table.
35 15 July ( St Swithun’s Day)
St Swithun’s Day, if thou dost rain,
for forty days it will remain;
St Swithun’s Day, if thou be fair,
for forty days ’twill rain na mair.
Although this is a familiar saying, its application
is not widely understood. In the hot, dry summer
of 1976 and the wet autumn of 2000, UK residents
experienced similar weather conditions, day after
day, for forty or more consecutive days. The
implication of this rhyme is that if a rainy trend has
become established around 15 July, it is likely to
continue until the end of August. A second, less wellknown, implication of the rhyme is that a dry trend,
established around the same date, will also continue
for roughly the same period. For most of my male
forebears, St Swithun’s Day was one of the most
important in the farm calendar because it predicted
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the general character of weather conditions likely to
prevail throughout the cereal harvest. In most years,
however, this rhyme was not applicable. You could
only use it on 15 July if, on that day, there was a
period of continuous precipitation or a long period
of unbroken sunshine, with barely a cloud in the sky.
From your observations of weather conditions
(hot, cold, wet, dry) on 15 July, make a prediction
about the general trend the weather will show during
August. Evaluate your prediction using daily records
of midday temperatures and hours of sunshine
throughout that period.
If the conditions in this rhyme are met on
Michaelmas Day, for how many more days does it
remain dry with frost at night?
36 31 August
Don’t let Jack Frost reap your harvest.
Frosts may occur at any time after the end of August.
This saying serves as a reminder that frost-tender
fruits, such as runner beans, tomatoes, cucumbers
and marrows, should be gathered before they are
damaged by frost. The same applies to certain
flowers, notably dahlias and begonias, in which
aerial shoots of the plant can be cut back (reaped) to
ground level by a severe frost.
Using a maximum–minimum thermometer, record
the earliest date on which a night temperature below
0 °C was recorded. Was the first frost of autumn
severe enough to blacken runner bean leaves, or to
‘reap’ dahlias and begonias back to ground level?
37 21 September (autumn equinox)
This equinox coincides with a time when mature
root crops are harvested. Some of these, including
beetroot and onions, would be pickled in vinegar on
or around this date. If you wanted to store hazelnuts
for the winter, they should not be picked before the
equinox, or otherwise the kernels would shrivel.
Collect batches of 20 hazelnuts at weekly
intervals during September. Weigh each batch and
record their mass. Store each batch in an open dish
or bowl until January, and then re-weigh them and
record their mass. Calculate percentage loss of mass
for each batch. Crack the nuts; extract and weigh
the kernels. Which week of September is best for
collecting nuts to keep until Christmas?
38 29 September (Michaelmas)
If Michaelmas sets clear and bright,
it will stay dry with frost at night.
Fields in which cereals and root crops had been
grown were often ploughed at the end of September.
In order to do this effectively, farmers needed dry
weather. This saying indicates that if a high-pressure
system was determining the weather on Michaelmas
Day, there was a good chance that the dry spell
would continue for several more days.
39 18 October (St Luke’s Day)
Early leaf fall: hard winter
Late leaf fall: mild winter.
The reference point for this saying was taken as
St Luke’s Day, when in an ‘average’ year half the
leaves of deciduous trees were supposed to have
fallen. Neither the oak nor the beech was regarded
as a good indicator. It was best to look at other trees
such as cherry, sweet chestnut, horse chestnut, silver
birch and ash to determine what the weather was
going to be like in the period leading up to Christmas
(Figure 7).
Figure 7 A liquidambar tree in December. The
persistence of autumn leaves on trees beyond the
end of October was taken as a sign that the coming
winter would be mild.
In mid-October examine a number of trees and
estimate whether their leaf canopy is still 25, 50,
75 or 100 per cent intact. Record your results and
calculate mean values for each tree species. Make
a prediction about the nature of the coming winter
and evaluate it by comparison with mean midday
monthly temperatures during November–April.
109
‘St Luke’s little summer’, a period of fine, warm
sunny weather that often occurs around this time of
year, offered a good opportunity for farmers to pick
apples or lift any remaining root crops.
From your records is there a period of warm, dry
conditions between 10 and 25 October that could be
called a ‘little summer’?
41 Phases of the moon
Sow seeds and plant crops in the face of the moon.
Sowing and planting by phases or ‘faces’ of the moon
is an ancient custom, believed to have been practised
in some rural communities for more than 2000 years.
Viewed from the earth the moon appears to change
shape, with a complete cycle of changes every 29
days. What viewers actually see are changes in
portions of the moon illuminated by sunlight. Each
moon cycle has four phases, called ‘quarters’. During
the first two the small, crescent-shaped ‘new’ moon
appears to increase in size, or wax, until it forms a
spherical ‘full’ moon. During the last two phases the
moon wanes, gradually decreasing in size until it
once again takes on the appearance of a ‘new’ moon
(Figure 8).
Accumulated folk wisdom dictates that you
should sow plants with seed-bearing capsules
(lettuce, cabbage, broccoli) at the first quarter. The
full moon, and the days that follow it, are the best
time for sowing seeds of plants that bear legumes
(peas, beans), cereals (wheat, oats, barley) and berries
(tomato, cucumber, marrow). An ancient rhyme,
recorded in the 16th century, reads as follows:
40 Good Friday and Christmas Eve
Plant your potatoes on Good Friday and your
shallots on Christmas Eve.
This saying may relate to the belief that blessings
given at major Christian festivals extended to crops
planted in the fields. A more important question is
whether or not potatoes and shallots, planted at these
times, produce better yields than those planted, say,
one month earlier or one month later.
In order to find out, purchase a bag containing
at least 15 ‘seed’ potatoes. One month before Good
Friday, plant one of these in each of five large flower
pots, using either sterile loam or potting compost
as a growth medium. Set up a further five pots of
potatoes on Good Friday and another batch one
month later. Water and weed the plants and keep
them, as far as possible, under similar conditions. At
the end of July remove, wash, dry and weigh the new
potatoes produced by each batch. Compare masses
to test the validity of the saying. What other factors
do you think might have influenced your results?
Sow peas on and beans in the wane of the moon,
Who soweth them sooner, he soweth too soon.
wa
in
n
g
full moon
1st quarter
3rd quarter
ax
ng
new moon
w
Figure 8 Phases of the moon.
110
Freeland
At the third quarter, root crops (turnips, carrots, beet)
should be sown along with potatoes, onions, trees
and shrubs. Those who adhere to these practices
believe that the waxing moon has a generally
stimulating effect on plant-shoot growth, whereas
a waning moon favours the growth of roots. For
the best results, specific crops should be sown and
harvested on specific dates. Among the reasons
given by practitioners is that each crop type is linked
to one or more signs of the zodiac. Optimal dates for
planting are calculated by reference to these signs
and astronomical calendars. Inevitably, the first
question asked by scientists is whether or not there is
any scientific basis for these practices. No decisive
answer is currently available. However, phases of
the moon exert a marked influence on tides. They
may also exert some influence on the level of water
tables in soils, the highest levels coinciding with the
highest tides. Claims are also made that dry seeds
will absorb more water at ‘full’ moon than at other
times during the lunar cycle. This is said to result
in seeds of peas, sown at this time, producing more
vigorous seedlings.
Carry out your own experiment by sowing 20 or
25 seeds of any of the plants listed above in a garden
plot, not pots, at each of the four phases of the moon.
Compare growth rates and yields at harvest. What
other factors might affect your results? Devise and
carry out an experiment to find out whether dry pea
seeds absorb more water at ‘full’ moon than they do
at other times.
General references
Giles, Bill (1990) Story of weather. London: BBC
Publications.
Simpson, J. (1973) The folklore of Sussex. London: Batsford.
Tusser, T. (1562) Five hundred points of goode husbandry.
Useful websites
www.bbc.co.uk/weather
www.coldal.org/weather.htm
www.scoutingresources.org.uk/weather_lore.html
Summary
The rhymes and sayings listed above represent
only a small part of the country lore farmers and
gardeners in the 19th and early part of the 20th
century would have used to predict the weather. It
would be a great pity, of course, if this accumulated
wisdom were to be forgotten as a result of being
replaced by more accurate, reliable methods of
weather forecasting. While survival is no guarantee
of truth or effectiveness, some of these sayings and
rhymes do contain important insights, while others
have little or no predictive value. Budding scientists
may be motivated to find out which ones, if any, are
useful for predicting the weather.
Peter Freeland is a retired head of science living in Sussex.
111

Testing weather lore in school

Transcription

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