 Cloud often forms inland , especially near hills , and reduces exposure to sunshine . The average annual sunshine totals around 1 @,@ 600 hours . Rainfall tends to be associated with Atlantic depressions or with convection . In summer , convection caused by solar surface heating sometimes forms shower clouds and a large proportion of the annual precipitation falls from showers and thunderstorms at this time of year . Average rainfall is around 800 – 900 mm ( 31 – 35 in ) . About 8 – 15 days of snowfall is typical . November to March have the highest mean wind speeds , with June to August having the lightest . The predominant wind direction is from the south @-@ west . 
