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Details available for: sunshine
- rainfall - wind
- temperature - snow
- visibility
See also Scotland
- Wales
- Northern
Ireland climates.
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The sunniest parts of the United Kingdom are along the
south coast of England. This is largely because the formation
of convective (cumulus) cloud takes place over land and
skies over the sea remain cloud-free. Many places along
this south coast achieve annual average figures of around
1,750 hours of sunshine. The dullest parts of England are
the mountainous areas, with annual average totals of less
than 1,000 hours.
Mean daily sunshine figures reach a maximum in May or June,
and are at their lowest in December. The key factor is,
of course, the variation in the length of the day through
the year, but wind and cloud play their part as well.
Facts and figures (bright sunshine)
Maximum duration in a month: 383.9 hours at Eastbourne
(East Sussex) in July 1911.
Minimum duration in a month: 0.0 hours at Westminster (Greater
London) in December 1890.
Sunshine
graph
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Rainfall in England varies widely. The Lake District is
the wettest part, with average annual totals exceeding 2,000
mm (this is comparable with that in the western Highlands
of Scotland). The Pennines and the moors of south-west England
are almost as wet. However, all of East Anglia, much of
the Midlands, eastern and north-eastern England, and parts
of the south-east receive less than 700 mm a year.
Typically, it rains on about one day in three in England,
perhaps somewhat more often in winter, though long, dry
spells occur in most years.
Near the south coast there is an appreciable summer minimum
and winter maximum of rainfall, with totals in July barely
half those in January; western, northern and eastern coasts
are more likely to see the driest month in spring and the
wettest in late autumn. Inland, parts of the Midlands experience
a summer rainfall maximum, which is a reflection of the
higher frequency of thunderstorms in the more central and
south-eastern parts of England. For example, at London and
Birmingham, thunder occurs on an average of 15 days a year,
but in the west and north-west the frequency declines to
around eight days per year.
Facts and figures
Maximum in a day (09-09 UTC): 279 mm at Martinstown (Dorset)
on 18 July 1955.
Rainfall
graph
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There is a close relationship between surface
isobars (lines joining points of equal air pressure) and
wind speed and direction over open, level terrain. However,
in mountain and moorland areas such as the Pennines, local
topography also has a very significant effect with winds
tending to be aligned along well-defined valleys. The most
common direction from which the wind blows in England is
the south-west, but in a climate which is extremely variable
from day to day, winds from other directions are quite frequent
and long spells of easterly or north-easterly winds are
not unusual.
Over land, the roughness of the ground causes
a decrease in the mean wind speed compared with that which
occurs over the sea, with the size of the decrease depending
on the nature of the terrain. In major towns and cities
the overall mean speed is considerably reduced by the buildings,
but local funnelling may occur and the wind can gust to
about the same speed as in open country. It is this gustiness
which causes much of the damage to buildings and trees on
really windy days, though such days are comparatively rare.
A day of gale is defined as a day on which
the mean wind speed at the standard measuring height of
10 m about ground attains a value of 34 knots (39 miles
per hour, 17.2 metres per second) or more over any period
of 10 minutes during the 24 hours. The strongest winds in
the United Kingdom are associated with the passage of deep
depressions across or close to the British Isles; these
are most frequent during the winter, so that is when gales
are most likely. These depressions are usually at their
most intense over the open Atlantic Ocean; thus at low altitudes
gales occur most frequently on the exposed western and northern
coasts of both Britain and Ireland. For example, the Hebrides
experience, on average, about 35 days of gale a year. In
England, because of the protection afforded by Ireland,
the most exposed coasts are those of Devon and Cornwall,
and here there are about 15 days of gale a year. Inland,
the number of days decreases to fewer than five days a year.
In general, wind speed increases with height,
with the strongest winds being observed over the summits
of hills and mountains. Wind data at high altitudes in England
are very sparse, and it is not possible to quote data for
the full 30-year period 1961-90; as an indication, however,
Great Dun Fell in Cumbria (at 857 metres) averaged 114 days
of gale a year during the period 1963 to 1976.
Facts and figures
Highest gust recorded at a low-level site:
103 knots (118 m.p.h.) at Gwennap Head (Cornwall) on 15
December 1979.
Wind
graph
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Over England the mean annual temperature at low altitudes
varies from about 8.5 °C to 11 °C, with the highest values
occurring around or near to the coasts of Cornwall. The
mean annual temperature decreases by approximately 0.5 °C
for each 100 m increase in height so that, for example,
Great Dun Fell in Cumbria (at 857 m) has an annual mean
temperature of about 4 °C.
To a very large extent, winter temperature in the British
Isles in influenced by the surface temperatures of the surrounding
sea, which reach their lowest values in late February or
early March. Around the coasts February is thus normally
the coldest month, but inland there is little to choose
between January and February as the coldest month.
The coldest nights are those on which there is little wind,
skies are clear, and there is a covering of snow on the
ground; the lowest temperatures occur away from the moderating
influence of the sea, on the floors of inland valleys into
which the cold air drains. It was under such conditions
that the temperature fell to -26.1 °C, the lowest ever recorded
in England, at Newport in Shropshire on 10 January 1982.
Coastal areas do not experience such cold nights; as an
example the lowest temperature ever recorded at Plymouth
in Devon is -8.8 °C on 2 January 1979. At the opposite extreme,
the highest winter temperatures are apt to occur in the
lee of high ground. These high winter temperatures (up to
16 °C on rare occasions) occur when a moist south to south-westerly
airflow warms up downwind after crossing mountains, an effect
knows as the föhn after its more dramatic manifestations
in the Alps.
July is normally the warmest month in England, and the
highest temperatures of all have occurred in central districts
furthest away from the cooling influence of the Atlantic.
The highest temperature ever recorded in England is 38.5 °C
at Brogdale, near Faversham in Kent on 10 August 2003, which
is also the highest temperature ever recorded anywhere in
the United Kingdom.
Facts and figures
Air temperature (measured under standard conditions at
1.25 m above the ground).
Highest recorded 38.5 °C at Brogdale, near Faversham
in Kent on 10 August 2003.
Lowest recorded -26.1 °C at Newport (Shropshire) on 10
January 1982.
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Snow is comparatively rare near sea level in England, but
much more frequent over hills. The average number of days
each year when sleet or snow falls in England varies from
about 10 or less in some south-western coastal areas to
over 50 in the Pennines. Snow rarely lies on the ground
at sea level before December or after March, and the average
annual number of days with snow lying in England varies
from five or less around the coasts to over 90 in parts
of the Pennines. A day of snow lying is defined as one with
snow covering at least half of the ground at 0900 UTC.
The number of days of snowfall and snow cover varies enormously
from year to year. At many places in the last fifty years
it has ranged from none at all in a number of winters to
in excess of 30 days during the winters of 1946/47 and 1962/63.
Even places near the coast experienced prolonged snow cover
during these two winters. In heavy snowfalls there can be
quite extensive drifting of the snow in strong winds, especially
over the higher ground, resulting in severe dislocation
of transport. Fortunately such occasions are comparatively
rare.
Facts and figures
Snow graph
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Many parts of England, especially those relatively remote
from the industrial and populous areas of both Britain and
mainland Europe, enjoy good visibility. This is particularly
true of much of the coastline, the mountains and the moorlands.
Over high ground in England fog statistics are scarce,
but because moist air often spreads across the country,
hill fog can be both extensive and frequent and is a potential
hazard to be borne in mind by walkers. Contrast the average
233 days of fog a year at 0900 UTC between 1963 and 1976
at Great Dun Fell in Cumbria (at 857 metres), with the 1961-90
figure of six days for Carlisle (at 26 metres) in the same
county.
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