Britain endured its hottest night ever recorded on Monday as temperatures are predicted to rise even further on Tuesday and hit 40C in some areas.
Following the hottest day of the year on Monday, temperatures didn't fall below 25C in parts of the country into the evening.
This exceeds the previous highest daily minimum record of 23.9C, recorded in Brighton on August 3, 1990, making it "provisionally the warmest night on record", according to the Met Office.
Monday's temperatures broke several records after mercury peaked at 38.1C in Santon Downham, Suffolk, making it the hottest day of the year so far and the third hottest day on record, after 38.7C in Cambridge in 2019 and 38.5C in Faversham, Kent, in August 2003.
Tuesday is set to get even hotter as travel chaos continues with further cancellations and delays due to the melting temperatures.
Mercury will sizzle at possible highs of 41C in isolated areas on Tuesday, making the country hotter than Jamaica, the Maldives and Barbados.
Rachel Ayers, a Met Office forecaster, said Tuesday will be a "pretty unprecedented day".
She said: "The temperature will be very hot throughout the day, before rising as high as 40C, maybe even 41C in isolated spots across England during the afternoon.
“This will make it the hottest day on record and the first time we have seen temperatures as high as 40C.”
Transport Secretary Grant Shapps said issues on the rails and roads will continue for decades during scorching heatwaves and conceded the UK’s transport network - much of it built during the Victorian era - was not built to cope with the extreme heat.
He urged people to “apply common sense” and “depending on the nature of your journey and reason for it, you might want to consider rearranging your day around it”.
Asked how long it will take to upgrade existing rail infrastructure to be more resilient, Mr Shapps told Sky News: “Decades, actually, to replace it all. Ditto with tarmac on the roads.
“There’s a long process of replacing it and upgrading it to withstand temperatures, either very hot or sometimes much colder than we’ve been used to, and these are the impacts of global warming.”
Most routes across England and Wales will be affected by the hot weather on Tuesday, according to National Rail, with customers told only to travel if “absolutely necessary”.
Network Rail said: “There will be delays, cancellations and last-minute changes to train services due to the unprecedented record heat on those days.”
The RAC anticipated that the number of vehicle breakdowns on Monday and Tuesday could be up to a fifth higher than normal.
“This could pose a significant health risk to those stuck on services or roads during the heat," added Met forecaster Ms Ayers.
Scotland could also see its hottest day ever on Tuesday and Wales could smash historic temperatures for the second day running, after seeing its hottest day on record on Monday with temperatures reaching to 37.1C in Hawarden, Flintshire.
There have been warnings of pressures on hospitals from the extreme temperatures, and concerns ambulance services would face rising numbers of calls as the heat peaks on Tuesday afternoon.
Water companies have been experiencing “unprecedented peak demand”, with people encouraged to “carefully consider” their water usage and urged not to waste it.
There are also warnings of wildfires, after fire crews tackled a large blaze at Lickey Hills Country Park, South West of Birmingham, covering at least 5 hectares believed to have been sparked by a disposable BBQ.
People are being asked not to use barbecues or leave litter that could spark further fires in the countryside, while zoos and wildlife parks were closed to protect animals, staff and visitors.
The Department for Environment, Food and Rural Affairs (Defra) has a high pollution alert in place in the eastern parts of England and the East Midlands, meaning EU ozone pollution thresholds have been exceeded.
The UK Health Security Agency has issued a level 4 heat-health alert – described as an “emergency” – and the UK is under its first red extreme heat warning for a large part of England, issued by the Met Office.
Britons have been urged to stay inside during the hottest period of the day, between 11am and 4pm, and wear sun cream, a hat, stay in the shade and keep hydrated with water – and there are warnings about swimming in lakes, rivers and reservoirs.
Emergency services and the government have reiterated urgent warnings about the dangers of trying to keep cool after several tragedies in waterways and reservoirs during the heatwave.
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A 14-year-old boy is missing and believed to have drowned on Monday afternoon after getting into difficulty in the Thames in Richmond, west London.
The teenager was seen entering the water at Tagg’s Island in Hampton and, after a search took place, he was presumed dead, with officers calling the incident a “tragedy”.
It came as the family of 13-year-old Robert Hattersley said they were “absolutely devastated” after he died when he got into trouble in the River Tyne in Northumberland on Sunday.
Emergency services also confirmed the deaths of a 16-year-old boy in Salford Quays, Greater Manchester, a 16-year-old boy in Bray Lake near Maidenhead, Berkshire, and a 50-year-old man in a reservoir near Leeds in similar circumstances.