The UK has recorded its hottest-ever May temperature as the mercury rose to 34.8C in Kew Gardens in south-west London.
Many other areas in the south-east of England also reached temperatures in the 30s.
BBC Weather said highs expected in parts of the UK on Monday and Tuesday could exceed top temperatures in Lagos, Cairo and Ho Chi Minh City.
The Met Office said the heat would be "exceptional in the UK even in mid-summer, let alone in May".
An amber health alert issued by the UK Health Security Agency (UKHSA) also remains in place warning that there is a risk of a significant impact across health and social care services.
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Cooling down on Bournemouth's beaches
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The NHS warned people to keep hydrated, with babies, children and older adults at the highest risk of dehydration
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A picture-perfect view of Greenwich park in south-east London
BBC Weather Watchers/ Lucie Johnson
Punts on the River Cherwell in Oxford
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A field red with poppies in Salthouse, Norfolk
BBC Weather Watchers/ Linda's Local
Cows seeking shade under a tree in a field in Crook of Devon, Perth and Kinross
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Taking a rest at the Trentham Monkey Forest in Tittensor, Stoke-on-Trent
BBC Weather Watchers/ Lord Tenby
In Wales, people flocked to Tenby North Beach in Pembrokeshire
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A birdseye view of beachgoers in Falmouth, Cornwall
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A boy makes his selection at a beach stall in Southend
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Convertible car weather in Rosedale Abbey, North Yorkshire Moors
BBC Weather Watchers/ Danny McGuigan
This feathered family was on the move in the sunshine
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Two families enjoying the views in Rosedale Abbey, North Yorkshire
BBC Weather Watchers/ Silverloon
Charity Age UK recommended staying inside during the hottest hours of the day
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In Pictures via Getty Images
BBC Weather Watchers/ Lucie Johnson
BBC Weather Watchers/ Walking Tractor
BBC Weather Watchers/ Linda's Local
BBC Weather Watchers/ Pauls Camera
BBC Weather Watchers/ Lord Tenby
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BBC Weather Watchers/ Danny McGuigan
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BBC Weather Watchers/ Silverloon