The UK is expected to get even hotter with temperatures predicted to reach a sizzling 32C (89.6F).
Records were set in both England and Wales on Sunday, and the mercury is forecast to climb even higher on Monday.
In England on Sunday, 31.6C (88.88F) was recorded in Heathrow, overtaking Saturday’s record-breaking 30.3C (86.54F) recorded in Coton in the Elms, Derbyshire.
Wales recorded 30.2C (86.36F) in Cardiff, compared with 29.6C (85.28F) reached in Usk, Monmouthshire, on Saturday.
Police said a body was recovered from a lake in Sheffield and a man died after falling from rocks in Dorset, taking the number of deaths linked to the warm weather on Sunday to five.
South Yorkshire Police said emergency services were called to Crookes Valley Park shortly after 7.30pm on Sunday following calls that a man had got into difficulty in a lake.
An underwater search team discovered a body in the water just before midnight, with formal identification yet to take place, the force added.
Meanwhile, Dorset Police said emergency services were called at 6.30pm on Sunday to reports that a man had fallen off rocks at Stair Hole near to Lulworth Cove in the Purbeck area.
The man was pronounced dead at the scene and his family have been informed, according to the force, which added that there were no suspicious circumstances.
Two teenagers died in Greater Manchester and Oxfordshire on Sunday, along with a man in his 50s in North Yorkshire.
The Met Office said temperatures could climb to a maximum of 32C in London and the South East of England on Monday, adding that there is a low chance of isolated heavy showers in the afternoon.
The long range forecast for next weekend suggests spells of rain or showers are likely for many areas, with temperatures easing back closer to normal.
Forecasters also warn that some heavy rain or thunderstorms are possible.
Tens of thousands of people headed for beaches over the weekend with roads busy on coastal routes.
Saturday had marked the hottest day of the year for all four nations, and the hottest day since records began for Northern Ireland with 31.2C (88.16F) recorded in Ballywatticock, in Co Down, beating the previous highest temperature of 30.8C (87.44F), which was reached on July 12 1983 and June 30 1976.