The Met Office has provisionally recorded a new maximum temperature of 18.7C (65.66F) for December in the UK.
Forecasters took the measurement at Achfary in the Highlands on Saturday, which would be the hottest day of the month on record in Britain if validated.
It would beat the current top December temperature of 18.3C (64.94F), which was taken at Achnashellach in the Highlands in 1948.
A new provisional maximum temperature of 18.7 °C was recorded at Achfary in Scotland on the 28th December 2019
It will be quality controlled & if validated would be the highest temperature officially recorded in the UK during December pic.twitter.com/FXVMXvcR5I
— Met Office (@metoffice) December 31, 2019
The recording has been put down to a meteorological phenomenon known as the Foehn Effect.
This is a change from wet and cold conditions on one side of a mountain to warmer and drier conditions on the other side.
The most notable Foehn events tend to occur across the Highlands, where the moist prevailing westerly winds encounter high ground along Scotland’s west coast.
On Saturday, the northern part of Scotland was experiencing southerly winds.
The lowest temperature recorded on the same day was 1.7C (35.06F) in Writtle, Essex.