Last month was the third warmest March on record - outshone only by 1938 and 1957 - the Met Office has said.
It had an average temperature of 7.7C, compared with March 1938, which had an average of 8C. It was also the fifth driest and third sunniest March.
March saw a total precipitation of 36.4mm of rain and 156.5 hours of sunshine across the month.
Records for temperature and rainfall began in 1910, while the measurements for sunshine began in 1929.
The driest and the sunniest March both occurred in 1929, with just 17mm of rainfall and 169.5 hours of sunshine recorded.
England saw an average temperature throughout the month of 8.1C. Wales recorded 7.9C, Scotland 7C and Northern Ireland's was 8.1C. The average temperatures are measured across every hour of the day and night.
And during the month there were 175.4 hours of sunshine in England, 158.8 in Wales, 129.7 in Scotland and 127.5 in Northern Ireland.
Rainfall in England was 26.5mm with 31.4mm in Wales, 56.8mm in Scotland and 21.4mm in Northern Ireland.
The good weather saw Scotland set a new record for its highest March temperature three days in a row.
Aboyne in Aberdeenshire recorded 23.6C on Tuesday 27 March, beating the record of 23.2C set at Cromdale, near Grantown on Spey, the previous afternoon.
And the day before that, Fyvie Castle in Aberdeenshire recorded 22.8C, beating a March temperature record which had stood for 55 years.
The previous record March temperature in Scotland stood at 22.2C, recorded in 1957 at Gordon Castle, in Moray, and again at Strachan, in Kincardineshire, in 1965.
It was during March that seven water companies across southern and eastern England announced they were imposing water restrictions.
This came after the past two winters were unusually dry, leaving reservoirs, aquifers and rivers below normal levels.
With last month being the fifth driest March on record, water levels have not improved and so the hosepipe ban will begin on Thursday.