The number of hours of bright sunshine is controlled by the length of day and by cloudiness. In general, December is the dullest month and May or June the sunniest.
Sunshine duration decreases with increasing altitude, increasing latitude and distance from the coast. Local topography also exerts a strong influence and in the winter deep glens and north-facing slopes can be in shade for long periods. Industrial pollution and smoke haze can also reduce sunshine amounts, but the decline in heavy industry has resulted in an increase in sunshine duration particularly in the winter months.
Eastern Scotland includes the sunniest places in Scotland, these being on the coast of Fife where the average is about 1500 hours per year. Other coastal places, for example in East Lothian, average more than 1400 hours but sunshine averages are lower elsewhere, and are lowest over the Grampian mountains (less than 1100 hours). The sunniest places on mainland UK are along the south coast of England, with over 1750 hours per year on average, whilst the Channel Islands enjoy over 1900 hours.
The graphs show the average monthly sunshine totals for Dyce and Braemar, together with the highest and lowest totals recorded in the stated periods. The sunniest month is May, rather than June, because of the tendency for settled anticyclonic conditions in late spring which is a feature of the weather over Scotland as a whole. However, this national trend is less marked and even reversed at places close to the east coast because of the occurrence of sea-fog (haar) in late spring. Here, June is marginally sunnier than May.
