Already -17C at Kinbrace, -16C at a couple of sites in the eastern Highlands.
https://www.wunderground.com/wundermap
Deep snow, light winds and clear skies, with cold pools built up over several days, mean perfect conditions for extreme minima tonight across the north and east Highlands. However, uppers are already getting milder from the north, so the glens of the eastern Highlands may benefit from a higher rate of cooling than Sutherland.
Altnaharra paper attached.
Altnaharra min temp.pdf