THE CLIMATE OF YORK 17 



the period 1881-1915. From a map given by Dr. J. Glasspoole in 

 British Rainfall, 1925, p. 266, we may estimate the ' standard deviation ' 

 of annual rainfall as 17 per cent, of the normal yearly fall. The driest 

 three consecutive years — 1904, 1905 and 1906 — yielded a mean rainfall 

 equal to 88 per cent, of the normal — a figure which may be compared with 

 the standard value of 80 per cent, ordinarily adopted by water engineers. 

 Of the last ten years, four (1924, 1925, 1926 and 1929) have given an 

 annual fall appreciably below normal. This is a point of some interest 

 in view of the fact that in the same period the rainfall over England and 

 Wales as a whole has been excessive in every year except 1929. 



Temperature. 



Table II gives monthly and yearly averages of daily maximum, daily 

 minimum and ' mid-temperature ' (mean of maximum and minimum) 

 referred to the standard period 1881-1915, along with particulars of the 

 highest and lowest readings in each month from 1871 to 1930. The 

 means for the year may be compared with similar data for other low-lying 

 inland towns : 



I 



The mean monthly data call for no special comment. In regard to the 

 extremes it is interesting to note that 60° has been reached in every month 

 of the year, and that readings below freezing point have occurred in 

 every month except June, July and August. The highest summer 

 temperatures are a trifle low for an inland station. The situation of the 

 station renders it rather liable to low minima, and we see that a reading of 

 zero Fahrenheit occurred in 1879. A further point of interest is that in 

 most months the extreme minimum occurred during the thirty years 

 preceding 1900, and the extreme maximum in the thirty years subsequent 

 to 1900. The same year, 1921, yielded both the highest and lowest 

 readings in July. 



The long series of observations at York provides an opportunity of 

 investigating the vexed question of changes of temperature within the 

 period covered by living memory. I give below the mean values derived 

 from the observations during the two periods of thirty years — 1871-1900 

 and 1901-1930 — for January, July, and the year. 



