The occurrence of snow is linked closely with temperature, with falls rarely occurring if the temperature is higher than 4 °C. For snow to lie for any length of time, the temperature normally has to be lower than this. Over most of the area, snowfall is normally confined to the months from November to April, but upland areas often have brief falls in October and May. Snow rarely lies at lower levels outside of the period November to April.
On average, the number of days with snow falling is about 20 per winter along the coast but over 100 days over the Grampians. The number of days with snow lying has a similar distribution, with less than 10 along the East Lothian coast but over 60 days over the higher ground of Grampian. These averages can be compared with the coasts of SW England where less than 3 days per year have lying snow.
The relatively plentiful supply of snow over the highest ground has led to the development of skiing areas such as Cairngorm, the Lecht (Grampian) and Glenshee (near Braemar).
The monthly averages of days with sleet/snow falling and lying at Dyce and Balmoral are shown below (a day of lying snow is counted if the ground is more than 50% covered at 0900). Days of sleet/snow falling for Balmoral have been estimated from 1 km grids (to the nearest day), as this station is not manned 24 hours a day.
Heavy snowfalls can cause transport disruption. For example, a very cold easterly airstream in mid-January 1987 brought record snow depths to eastern Scotland and the Central Lowlands. Over 20 cm of level snow occurred widely inland from Aberdeen southwards and a few places had over 40 cm.
"