The Met Office said the UK has a new provisional record January temperature of 19.9C.
It said it had received a manual reading recorded at Achfary, a tiny community in Sutherland.
The Met Office said this exceeded an automated reading of 19.6C reported at Kinlochewe on Sunday.
If confirmed, the temperature would be higher than the 18.3C recorded both at Inchmarlo and Aboyne in Aberdeenshire on 26 January 2003.
Sunday's high temperatures came during weather conditions known as the Foehn effect.
The weather involves a change from wet and cold conditions one side of a mountain area to warmer and drier conditions on the other side.