Cloud often forms inland, especially near hills, and reduce the amount of sunshine that reaches the park. The average annual sunshine is about 1,600 hours. Rainfall tends to be associated with Atlantic depressions or with convection. In summer, convection, caused by the sun heating the land surface more than the sea, sometimes forms rain clouds and at that time of year a large proportion of the rainfall comes from showers and thunderstorms. Annual precipitation varies from in the east of the park to over at The Chains. However, in the 24 hours of 16 August 1952, more than of rain fell at The Chains. This rainfall, which followed an exceptionally wet summer, led to disastrous flooding in Lynmouth with 34 dead and extensive damage to the small town.