Last December was the warmest on record dating back 350 years, forecasters at the Met Office havediscovered.
It was also the rainiest month on record for more than a century, while 2015 ranked as the seventh wettest year ever recorded.
"The weather during 2015 contained many notable features and I’m sure that everyone will have a personal memory of a weather moment during the year," said head of the National Climate Information Centre Dr Mark McCarthy.
"Sadly, for some, the extreme rainfall during December has left a legacy of flooding for communities across northern England, and Scotland. Elsewhere there were some brighter spots including the sunniest April on record for the UK.”
Last year was already the hottest on record globally, according to scientists, but the latest analysis identifies the trends of the UK climate specifically. The scientists found 2015 was the sixteenth warmest on record, based on figures which date back to 1910.
Read more: That was the hottest January ever recorded
However, temperature records which date back to 1659 (the longest running temperature data series in the world), show December was the mildest ever in modern history.
In terms of rainfall, the record was largely down to severe storms and flooding in specific areas, largely in the north of England, Scotland, Wales and Northern Ireland, caused by a string of high category storms, while other locatiosn in the country experienced rainfall that was below average.