The Met Office said the temperature soared to 27.6C at 2.27pm at Heathrow in west London on Saturday. That beat 2019's previous warmest temperature of 25.8C, which was set last month. June 1 is treated by weather experts as the meteorological first day of the UK summer.
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Areas in the south east of England have enjoyed the best of the weekend weather so far, with Teddington in south-west London and Wisley in Surrey seeing the mercury rise to 26.4C.
The temperature also reached 26C in High Beach, Essex, and 25.9C at the Iver water works in Buckinghamshire.
Conditions could get even hotter in East Anglia on Sunday, with temperatures of 28C or 29C expected, but that could also bring a risk of thunder.
Met Office meteorologist Emma Smith said
