Some parts of England and Wales could see temperatures of up to 30 degrees
Britain has enjoyed the hottest day of the year so far as the mercury rose above 30C.
The warmest temperature was recorded at Eton Dorney Lake in Buckinghamshire, where the thermometer soared to 30.2C (86F).
St James's Park in central London and Charlwood, close to Gatwick Airport in Surrey, saw temperatures hit 30.1C and 30C respectively.
It beats the previous highest temperature of 29.3C (84.74), which was recorded in Achnagart, in the Highlands, on May 25.
The outlook for the rest of the week is good news for organisers of the London Olympics, as the hot and dry conditions are set to prevail during Friday's opening ceremony.
Helen Rossington, a forecaster for MeteoGroup, the weather division of the Press Association, said: "At the moment it is looking like the only risk of showers on Friday will be in the evening, at 5pm or 6pm, so if there is rain it should be before the opening ceremony starts at 9pm.
"Tomorrow is going to be similar to today, with temperatures of 28C (82.4F) expected in central London.
"The south of England will see temperatures of 25C (77F) on Friday, but things will start to cool down again on Saturday as we return to temperatures of 20C (68F)."
The predicted drop may be a blow to sun lovers, but rail commuters are likely to see it as a blessing after some Greater Anglia services were disrupted by today's hot weather.
The train operating company implemented speed restrictions and cancellations as older sections of overhead lines can expand and sag in high temperatures.