 Typically , the warmest day of the year ( 1971 – 2000 ) will achieve a temperature of 26 @.@ 6 ° C ( 80 ° F ) , although in June 1976 the temperature reached 31 @.@ 6 ° C ( 89 ° F ) , the site record . On average , 4 @.@ 25 days of the year will report a maximum temperature of 25 @.@ 1 ° C ( 77 ° F ) or above . During the winter half of the year , the coldest night will typically fall to − 4 @.@ 1 ° C ( 25 ° F ) although in January 1979 the temperature fell to − 8 @.@ 8 ° C ( 16 ° F ) . Typically , 18 @.@ 6 nights of the year will register an air frost . 
