Britain: An official handbook > 1956

THE BRITISH ISLES
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westerly ones. In hilly country wind direction may differ markedly from the
general direction owing to local effects. Winds are generally stronger in the north
than in the south of the British Isles, on the coasts than inland, and in the west than
in the east. The strongest winds usually occur in the winter; the average speed at
Kew Observatory, on the western outskirts of London, varies from about 10-3
m.p.h. at 50 feet in January and February to a minimum in August of 7-5 m.p.h.
The stormiest region of the British Isles is along the north-west coast with about
40 gales a year; south-east England is the least stormy, with gales occurring on
about 18 days a year inland and 25 days on the Channel coast.
Temperature. At stations near sea level the mean annual temperature ranges from
450 F. in the Hebrides to 520 F. in the extreme south-west; it is slightly lower in
the eastern part of the country in the same latitude. The mean monthly temperature
in the extreme north, at Lerwick (Shetlands), ranges from 390 F. during the winter
to 530 F. during the summer: the corresponding figures for Jersey (Channel Islands),
in the extreme south, are 430 F. and 63° F. The average range of temperature between
winter and summer varies from 150 F. to 230 F., being greatest at inland stations in
the eastern part of the country. During a normal summer, temperature occasionally
rises above 8o° F. in the south, but temperatures of 90° F. and above are uncommon.
Extreme minimum temperatures depend to a large extent on the environment,
but 200 F. may occur on a still, clear winter’s night, io° F. is rare, and o° F. or
below has been recorded only during exceptionally severe winters.
Rainfall. The British Isles as a whole have an annual rainfall of over 40 inches,
while England alone has just over 30 inches. The distribution of annual rainfall is
mainly determined by topography, the mountainous areas of the west and north
having far more than the plains of the south and east. Between 150 and 200 inches
of rain fall on the summits of Snowdon and Ben Nevis during the average year,
whereas some places in the south-east of England record less than 20 inches. Rain
is fairly well distributed throughout the year, but April, on the whole, is the driest
month, and December, with about twice as much, the wettest. A period of as long
as three weeks without rain is exceptional, and confined to limited areas.
Sunshine. The distribution of sunshine over the British Isles shows a general
decrease from south to north, a decrease from the coast inland, and a decrease
with altitude. During the summer the mean daily duration of sunshine varies from
five hours in western Scotland to eight hours in the extreme south-east of England;
during the winter, sunshine is at a minimum, with an average of 0-5 hours per day
in the neighbourhood of Ben Nevis (Scotland) and the Peak District (Derbyshire)
and 1 -5 hours in the south of England.
Vegetation
With its mild climate and varied soils, Britain has a diverse pattern of natural
vegetation cover. When the islands were first settled, oak woodland doubtless
covered the greater part of the lowland, giving place to thin forests of Scots fir on
higher or sandy ground, interrupted by extensive marshlands and perhaps some
open moorland. In the course of the centuries nearly all the forests have been
cleared so that forest and woodland now occupy only about 6 per cent of the surface
of the country. Midland Britain appears to be well wooded because of the numerous
hedgerows and isolated trees. The greatest density of woodland occurs in the north
and east of Scotland, in some parts of south-east England and in Monmouthshire
on the Welsh border.