REPORT ON METEOROLOGICAL OBSERVATIONS, WISLEY, 1917. 317 
into view the relation between the mean temperature of the air and 
its average daily variation (the mean maximum and mean minimum) ; 
Jan Feb 
MarAplMayJun tfw. AugSep OqtNovDeo 
3° 
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Fig. 50. — Temperature and Rainfall at Wisley, 191 7, as compared 
with the Average. 
and also the mean temperature of the ground surface where it is 
covered with short grass. 
The weather conditions for each month of the year may be sum- 
marized as follows : — 
January. — The spell of cold weather,^ which had been so marked 
a feature of the closing months of 1916, was abruptly broken near the 
close of December, and the New Year began with a brief interlude of 
unusual mildness. This came about under the influence of a south- 
westerly wind which blew for a few days, and brought with it maximum 
temperatures of between 50 0 and 60 0 in several parts of the kingdom, 
the highest recorded at Wisley being 53 0 . But the improvement 
was very short-lived, and by the close of the first ten days Arctic 
conditions had again become general all over the British Isles. In 
VOL. XLIII. y 
