UK weather: Hottest ever late-December temperature as mercury hits 16.8C in Scotland

Scottish Highlands hotter than Cyprus at 3am with overnight high of 16.8C recorded in Cassley

(Getty)

The Met Office recorded an “exceptional” overnight temperature of 16.8C in northern Scotland in the early hours of Sunday morning, a record high this late in the year.

The unusually warm temperature, the highest on record for 29, 30 or 31 December, was recorded at 3am in Cassley in Sutherland.

Northeastern England and northern Wales also experienced an unseasonably warm night, with temperatures hitting 13.3C in Chillingham Barns, Northumberland, and 11.5C in Rhyl.

Met Office forecaster Alex Burkill told Sky News: “It is pretty exceptional. We have never recorded a temperature that high this late in the month. What makes it more unusual was the temperature came at 3am.”

The record high for December was set at 18.3C in Achnashellach in the Scottish Highlands, and was recorded on 2 December 1948.

According to the Met Office, the phenomenon is due to a meteorological pattern called the Foehn Effect, which occurs regularly in mountainous areas.

It takes place when humid air hits one side of the mountain and is pushed upwards by strong winds, forming cloud and rain at the top of the mountain.

Dry air is then pushed down the other side of the mountain and gets hotter as it travels down.

The Foehn Effect can result in strong windstorms which can cause damage to property and infrastructure, and can be dangerous for mountain climbers.

The warmth it brings can also cause avalanches, glacial melt and downstream flooding, as well as disintegrating ice shelves.

However, regions that experience the Foehn Effect regularly also have longer crop-growing seasons and warmer, drier climates.