A dive team has recovered the body of a 15-year-old boy who went missing after getting into a lake in Lincoln.
Lincolnshire Police had received reports of Declan Sawyer having difficulty after entering Swanholme Lakes at 2.30pm on Sunday afternoon.
Declan's father Carl has paid tribute to a "funny and outgoing young man who loved his fishing and his football".
A statement added: "He had a very cheeky smile and the personality to match. He was very much loved by his friends and family, and will be missed dearly by many.
"We would like to raise awareness about children playing near any rivers or lakes in the hot weather. Please can all parents, friends and family make their children aware of the dangers surrounding water."
The incident happened as extreme weather in the UK led to hottest day in May ever recorded, with temperatures reaching 34.8C (95F) on Monday.
This is considerably higher than the previous peak of 32.8C (91F) reached in 1922 and 1944, with records normally only broken by just tenths of a degree.
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In Edinburgh, a large grass fire broke out in Holyrood Park near Arthur's Seat - sending a plume of smoke over the city.
Meanwhile, several runners were treated for heat exhaustion during the Edinburgh Marathon, with 16 people taken to hospital on Sunday.
Hundreds of customers across Kent, Sussex and Leicestershire were also left without water on the hottest day of the year so far.
Supply issues were blamed for the disruption, with some properties experiencing low pressure and taps intermittently running dry.
"As a result of the recent hot weather, we're seeing increased demand across our network and we're having to pump far more drinking water than usual," South East Water's incident manager Steve Benton said.
A total of 97 Met Office sites reached or surpassed 30C (86F) across the UK on Monday, which senior meteorologist Becky Mitchell described as a "huge number".
The highest heatwave threshold in the UK at this time of year is 28C (82.4F) and that applies to London and north of the capital towards Cambridgeshire.
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Forecasters believe that large swathes of southern England and Wales could see temperatures exceed 35C (95F) today - with 36C possible in places.
Thunderstorms may be sparked in the afternoon, which will affect how hot it gets.
Temperatures will start to gradually decline from the middle of the week but it will still be largely dry with sunny spells - with the high 20s expected in many areas.
If validated, the latest May record means seven of the 12 monthly highs have been set since 2003, the Met Office said.
A previous study by the forecasters found breaking that record "is around three times more likely now in our current climate than it would have been in a natural climate not impacted by greenhouse gas emissions".
This means that the once one-in-100-year event is now a one-in-33 event, it said.
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