It has been the hottest Easter Monday on record in all four nations of the UK, the Met Office has said.
England reached the highest temperature with 25C (77F) recorded at Heathrow, Northolt and Wisley.
Temperatures hit 24.2C (75.6F) in Kinlochewe in the Highlands, 23.6C (74.4F) in Cardiff and 21.4C (70.5F) in Armagh.
Saturday was the hottest day of the year so far with 25.5C (77.9F) recorded in Gosport, Hampshire.
Wales, Scotland and Northern Ireland also enjoyed their warmest Easter Sunday on record, with temperatures hitting 23.4C (74.1F) in Edinburgh and Cardiff and 21.7C (71.1F) in Armagh.
In England, temperatures reached 24.6C at Heathrow - not beating 2011's Easter Sunday record of 25.3C in Solent, Hampshire.
The warm weather is caused by high pressure, according to the Met Office.
The UK's warmest Easter temperature on record was 29.4C at Camden Square in London on Holy Saturday in 1949.
BBC Weather forecaster Helen Rossington said that the Easter heatwave would not continue much beyond the long bank holiday weekend.
Temperatures will be just above 20C on Tuesday and Wednesday will see much cooler, more showery weather.