Page:Weather Facts and Predictions.djvu/39

 The fall in the driest year will be one-third below the average; that in the wettest year one-third beyond. Therefore the fall in the wettest will be double that in the driest year.

And, therefore, an excess or defect of say 20 per cent, entitles us to call any particular year a “wet” or “dry” one as the case may be.

July, August, and October are the wettest months at most lowland stations, but December, January, and February, are the wettest in the mountainous districts.

The rainfall is more evenly distributed through the year at Western coast stations than it is at Eastern or dry stations, or it may be put in this way:—The heaviest of heavy falls, say in twenty-four hours, at a wet station, will not amount to 6 per cent. of the annual total, whilst at a dry station a heavy fall may amount to 10, 12, or 14 per cent. of the whole annual quantity.

The question whether the rainfall of England is increasing, diminishing, or remaining stationary, must be answered by saying that observations extending over more than 140 years show, if anything, a slight increase.

The average rainfall for all England is 31¼ inches; for near London 25 inches.

In the British Isles, rain falls on an average on 183 days during the year. On 90 of those days the fall will be less than one-tenth, yielding about 4 inches; and on 15 days will exceed ½ an inch, yielding about 11 inches.

It will happen at least once during a term of years, at some period or other, that there