Many flocked to parks and beaches as the mercury rose to a top temperature of 24.5C (76.1F) in St James’ Park in central London, compared to high teens in the Mediterranean holiday islands.
Temperatures were in the mid-20s in much of England and Wales while parts of western Scotland and Northern Ireland were not so lucky and were hit by wet and cloudy conditions.
Sheffield, Cambridge and Gravesend in Kent all enjoyed highs of 24.3C (75.74F) while Northolt in north west London reached 24.1C (75.38F).
It means that this May could still be on track to become the hottest ever, with bookmakers Ladbrokes slashing odds to 5/1 that the record set 60 years ago when temperatures got to 32.8C (91.04F) will be beaten.
Forecasters said that while much of England and Wales would enjoy another warm day tomorrow, the South West will see showers.
The rain is expected to spread north east through the country, with conditions becoming more unsettled as the week goes on.
Met Office forecaster Helen Roberts said: “We expect to see highs of around 24C (75.2F) again tomorrow in the South East but temperatures will start to fall elsewhere.
“By Wednesday temperatures will likely be in the high teens rather than the low 20s and then go back to averages for this time of year of around 16C (60.8F).”
Northern Ireland will see today’s rain potentially ease over night but could witness heavy showers tomorrow evening and into the night.
Meanwhile, Scotland is expected to see an improvement, with temperatures rising to 20C (68F) in Glasgow compared to 15C (59F) today.
However, the fine weather will give way to rain and thunderstorms tomorrow, with the first heavy showers arriving over the Pennines tonight.