The climate of a country or district is, briefly, the average weather
of that country or district, and it depends upon various factors,
all mutually interacting, upon the latitude, the temperature, the
direction and strength of the winds, the rainfall, the character of
the soil, and the proximity of the district to the sea.
The differences in the climates of the world depend mainly upon
latitude, but a scarcely less important factor is proximity to the
sea. Along any great climatic zone there will be found variations
in proportion to this proximity, the extremes being "continental"
climates in the centres of continents far from the oceans, and
"insular" climates in small tracts surrounded by sea. Continental
climates show great differences in seasonal temperatures, the winters
tending to be unusually cold and the summers unusually warm, while the
climate of insular tracts is characterised by equableness and also by
greater dampness. Great Britain possesses, by reason of its position,
a temperate insular climate, but its average annual temperature is
much higher than could be expected from its latitude. The prevalent
south-westerly winds cause a drift of the surface-waters of the
Atlantic towards our shores, and this warm-water current, which we know
as the Gulf Stream, is the chief cause of the mildness of our winters.
Most of our weather comes to us from the Atlantic. It would be
impossible here within the limits of a short chapter to discuss
fully the causes which affect or control weather changes. It must
suffice to say that the conditions are in the main either cyclonic
or anticyclonic, which terms may be best explained, perhaps,
by comparing the air currents to a stream of water. In a stream a
chain of eddies may often be seen fringing the more steadily-moving
central water. Regarding the general north-easterly moving air from
the Atlantic as such a stream, a chain of eddies may be developed in
a belt parallel with its general direction. This belt of eddies or
cyclones, as they are termed, tends to shift its position, sometimes
passing over our islands, sometimes to the north or south of them,
and it is to this shifting that most of our weather changes are
due. Cyclonic conditions are associated with a greater or less amount
of atmospheric disturbance; anticyclonic with calms.
The prevalent Atlantic winds largely affect our island in another
way, namely in its rainfall. The air, heavily laden with moisture
from its passage over the ocean, meets with elevated land-tracts
directly it reaches our shores--the moorland of Devon and Cornwall,
the Welsh mountains, or the fells of Cumberland and Westmorland--and
blowing up the rising land-surface, parts with this moisture as
rain. To how great an extent this occurs is best seen by reference
to the map of the annual rainfall of England on the next page, where
it will at once be noticed that the heaviest fall is in the west,
and that it decreases with remarkable regularity until the least fall
is reached on our eastern shores. Thus in 1906, the maximum rainfall
for the year occurred at Glaslyn in the Snowdon district, where 205
inches of rain fell; and the lowest was at Boyton in Suffolk, with a
record of just under 20 inches. These western highlands, therefore,
may not inaptly be compared to an umbrella, sheltering the country
further eastward from the rain.
The above causes, then, are those mainly concerned in influencing the
weather, but there are other and more local factors which often affect
greatly the climate of a place, such, for example, as configuration,
position, and soil. The shelter of a range of hills, a southern aspect,
a sandy soil, will thus produce conditions which may differ greatly
from those of a place--perhaps at no great distance--situated on a
wind-swept northern slope with a cold clay soil.
Berkshire is an inland county but no part of it is as much as 75
miles from the coast. The chalk downs have a fine bracing climate, and
though some of the valleys may be relaxing and some of the moorland
tracts bleak, the general climate of the county is exceedingly
healthy. Compared with the south coast of England Berkshire is rather
cooler, with somewhat less sunshine and less rain than the coast.
Temperature, it should be remarked, varies according to height above
sea level, falling about 1° Fahr. for each 100 to 300 feet upwards. In
a comparatively level district, like Berkshire, this is not a very
serious consideration. The mean temperature for the year varies
in different parts of England from about 47·3 in the north-eastern
counties to about 49·6 in the south-east. The mean temperature is
about 49·0 in northern Berkshire and about 47·5 in south-western
Berkshire. It may be of interest to give the mean temperature for one
year at places in and close around Berkshire. We take the year 1907 and
the figures are as follows--Maidenhead 49·4, Wokingham 47·7, Swarraton
in Hampshire 47·9, Marlborough in Wiltshire 47·4, and Oxford 48·9.
The average temperature in the month of January varies from 37·0 to
38·0 in different parts of the county, and the average temperature
for July from 59·7 to 62·0.
In England bright sunshine is most prevalent on the coast and
decreases inland. The annual total amount for the south and east
coast from Cornwall to Norfolk is nearly 1800 hours, whilst in the
northern midland counties the amount is about 1200 hours. There
are no definite data available for giving the amount for Berkshire,
but there are probably about 1500 hours of bright sunshine in the year.
The rainfall varies a good deal in different parts of the county. The
amount is lowest in the north-east and highest in the south-west. Thus
Wallingford and Cookham have a rainfall of about 23 inches a year on an
average. At Reading, which is somewhat to the south-west, the amount
is nearly 24 inches a year, and on a line running through Wellington
College and Yattendon the amount is nearly 25 inches. Letcombe
Regis and Ashbury have a rainfall of between 25 and 26 inches. At
Faringdon the figure is above 26, and in the south-western corner of
the county there is a rainfall of about 29 inches a year. The average
yearly rainfall for the whole of England is 31·62 inches, and for the
British Isles it is 39·25 inches. Looking at the extremes of rainfall
in England we find the lowest at Shoeburyness with an average of 19·7
inches for the year, whilst Seathwaite in Cumberland has an average
rainfall of 133·53 inches per annum.