Britons are set for another scorcher as April's summer-like weather promises a balmy beginning to the weekend.
Thursday (April 19) was the hottest April day for nearly 70 years, with the mercury soaring to 29.1C (84F) in St James' Park in London.
Friday's highs are likely to be around 28C (82F) in the south-east, the Met Office said, with most parts enjoying warmer conditions than normal for the time of year.
"It's going to be pretty hot again tomorrow, with a lot of sunshine around," said meteorologist Alex Burkill.
"We will see highs of 26C, 27C and maybe 28C in the London area. Low 20s are likely for much of England and Wales, while Northern Ireland and eastern Scotland will see temperatures in the high teens."
All four home nations enjoyed their hottest day of the year so far on Thursday, with everywhere seeing a high of at least 20C (68F).
The hot weather, which is a result of warm air moving up from the Azores in the south, is set to last into the weekend.
The London Marathon is forecast to be the hottest yet, with a high of 23C (73F) possible, beating the 1996 record of 22.7C (72.9F).
Mr Burkill said: "It's going to be very hot and humid, and very close to, if not breaking, the record."
Race organisers have announced they will add more water, ice and shower stations along the 26.2-mile route.
Conditions may be especially difficult for fancy-dress runners, including the almost 100 attempting Guinness World Records dressed in outfits like a suit of armour, a Paddington Bear costume and ski boots.
Regular runners are being advised to consider dropping their goal times and to run more slowly.