The climate of Scotland is temperate, and tends to be very changeable. It's not uncommon to experience all four seasons in one day! The warmest months are July and August with temperatures at an average 17 °C. Rain falls throughout the year and April, May and June are normally the driest months. Annual rainfall in the western Highlands can be more than 3,000mm while the east coast receives an average of less than 800mm. The prevailing winds are from the west and southwest, and are a constant feature in the islands and Highlands.
Britain's Average Temperature, Rainfall and Sunshine hours
For more info, click on this link: http://www.metoffice.gov.uk/ and search for 'regional climate'.