Reading University weather expert reveals why the UK is suddenly mild after freezing temperatures

The coldest week since 2010 was recorded at the University of Reading’s Atmospheric Observatory last week, and now one of the university's weather expert has revealed why the weather has suddenly turned mild after freezing conditions.

Three separate temperatures of more than -5.0 °C were observed last week.

But conditions have significantly improved this week with a drastic rise in temperatures - reaching 12 °C in the early hours of Monday morning. (19 December)

This represents an “extraordinary rise of almost 20 degrees in a few days”, the University’s Dr Stephen Burt said.

According to Met Office data, temperatures in London will remain at 12°C throughout today (Monday, 19 December). The warmer weather is set to continue through to Christmas Day.

Dr Burt said the sudden surge in temperatures is down to a change in airmass.

He explained: “Very mild and humid Tropical Maritime air from the region of Madeira transported quickly north and eastwards to our islands because of the development of a major North Atlantic depression over the past couple of days.

"The tropical airmass displaced a cold and dry northerly airflow which persisted over the British Isles for most of last week, and several clear nights allowed widespread severe frost to develop.

“The British Isles often lies on the border between cold, dry Arctic airmasses and those originating from well south of our latitude, and such changes from very cold to very mild, or vice versa, are very much a feature of our winter climate - although not often with the degree or rapidity of the changes experienced within the past 24-36 hours.

“People will certainly welcome the reduction in energy bills as a result of this rapid transition.”

Dr Burt suggested drought restrictions could return next year after a lack of rainfall at the start of the month. However, 14mm of rain has been recorded at the University’s Observatory in the past 24 hours.

He added: “We've seen the first significant rainfall of the month. The first half of December was the driest such period on the University's records, which go back to 1908.

"The rainfall we’ve received over the past 24 hours represents just over a third of what we should have received by 19 December.”