 The average annual rainfall is 982 millimetres ( 38 @.@ 7 in ) in Orkney and 1 @,@ 168 millimetres ( 46 @.@ 0 in ) in Shetland . Winds are a key feature of the climate and even in summer there are almost constant breezes . In winter , there are frequent strong winds , with an average of 52 hours of gales being recorded annually in Orkney . <unk> wind farm on Shetland , which operates with five Vestas <unk> 660 kW turbines , achieved a world record of 57 @.@ 9 % capacity over the course of 2005 due to the persistent strong winds . 
