THE CLIMATE OF YORK 



21 



expressing the mean recorded sunshine in each month as a percentage of 

 the mean length of the day. Situated as the recorder is among the 

 chimneys of York, there is no doubt that the record is greatly affected by 

 local smoke obscuration. In December and January the mean duration 

 of sunshine bright enough to affect the Campbell-Stokes instrument is 

 under one hour per day — a value comparable with that found in large 

 manufacturing cities. During the summer months, however, sunshine is 

 relatively abundant, the mean values for June and July approximating 

 to those for Scarborough. The mean value for the year is distinctly low, 

 as will be seen from the following comparative data : 



Miscellaneous Phenomena. 



The last four columns of Table IV show the mean number of days of 

 occurrence of snow, snow lying at 9 h. over more than half the surrounding 

 country, hail, and thunderstorms. These means are based on the ten 

 years 1921-30. Snow occurs on about fourteen days a year, and thunder 

 on twelve — figures which indicate about the usual frequency of these 

 phenomena at low-lying inland stations in the North of England. 

 Thunderstorms are most frequent in July and August, when they occur 

 on about one day in ten, and rare in the winter months. Unfortunately, 

 statistics are not available from which to give similar tables for ground 

 frost and fog. 



I am indebted to the Director of the Meteorological Office for providing 

 facilities for the extraction of the data in this article from the official 

 records preserved in the Office. 



