December was the wettest month on record for the UK, provisional figures from the Met Office show.
The last month of 2015 was not only the wettest December on record, but the wettest calendar month overall in the records dating back to 1910.
It was also the UK's warmest December on record, with temperatures averaging 7.9C (46.2F), which is 4.1C (7.4F) above the long term average.
The month broke the record for the hottest average December by a full degree centigrade, beating the previous record set in 1934 of 6.9C, as the UK experienced temperatures closer to those normally seen in April or May.
The country saw almost double the amount of rainfall typically expected for the month with 230mm of rain - more than nine inches - falling on average across the UK.
Scotland and Wales had more than double their average rain for the month in December, while Northern Ireland experienced almost double the average, and England had 57% more rainfall than normal.
As the country was hit by storms and bands of heavy rain, clear, sunny days were in short supply, with less than three-quarters (73%) of the average number of hours of sunshine in December.
There was also virtually a complete lack of air frost across much of England, with the UK as a whole only experiencing an average of 2.6 days of frost in December - eight days below average.
Across 2015 as a whole, the year was the sixth wettest in the records dating back to 1910, largely due to unusually wet years in Scotland, Wales and north west England.
The average temperature of 9.2C (48.6F) for the UK in 2015 was "notably warm but not exceptional", falling short of 2014's record warmth, when temperatures averaged 9.9C (49.8F) across the year.