The temperature has hit 33.9C (93F) at Heathrow in west London, making it the hottest June day since 1976, the Met Office has said.
Temperatures are at their highest for a June day since the 35.6C (96F) recorded in Southampton on June 28 1976, and it is the warmest summer solstice on record.
The 40-year high has been recorded as parts of Britain swelter in the fifth consecutive day with temperatures above 30C (86F), in what is the hottest prolonged spell in June since the drought summer of 1976.
☀️We will reach the peak of the #heatwave today, with highs of 34 °C. For those who don't like the heat, it will feel much fresher tomorrow pic.twitter.com/1QsFLG3rwf
— Met Office (@metoffice) June 21, 2017
But there are also weather warnings in place for Wednesday afternoon and evening, with heavy rain and thunderstorms forecast for parts of southern Scotland, northern England, north Wales and the Midlands.
The Met Office warned of the potential for torrential downpours, frequent lightning, very large hailstones and strong gusts of wind, which could lead to localised flooding and temporary disruption of power supplies.
However, a cold front is set to sweep across the UK overnight into Thursday, bringing much more cloud and a fresher feel to the weather, the forecaster said.
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