London is predicted to be hotter than the Caribbean, the Western Sahara and popular holiday destinations in Europe as temperatures soar.
The Met Office has forecast the capital could see highs of 38C when the heatwave sweeps across England.
The rise in temperatures has forced the UK Health Security Agency to issue a level 4 heat-health alert – described as an “emergency” – while the Met Office has issued the UK’s first red extreme heat warning, with both running from Monday to Wednesday.
The capital’s scorching temperatures mean it will be warmer than Nassau in the Bahamas (32C), Kingston in Jamaica (33C), Malaga in Spain (28C), Athens in Greece (35C), Albufeira in Portugal (28C) and Dakhla, in the Western Sahara (24C).
Other areas of England will also experience hotter weather than the holiday destinations, with the Midlands predicted to see highs of 37C, East Anglia with 36C and the North West and North East with 33C.
It comes as new records were broken in Wales and Northern Ireland on Sunday.
Hawarden, a village in northern Wales, reached 33C while Armagh in Northern Ireland was 27.7C.
Tuesday is meanwhile predicted to be even hotter, with temperatures possibly reaching 40C – a new record for England.
Scientists at the Met Office have said the 40C prediction is a result of climate change, warning that the 40C figure “could be as much as 10 times more likely in the current climate than under a natural climate unaffected by human influence”.
Some schools in several counties, including Nottinghamshire and Hampshire, have confirmed they will close, while train companies urged people not to travel on Monday and Tuesday.
Network Rail will close the East Coast Main Line between noon and 8pm on Tuesday for all locations between London King’s Cross and York and Leeds, with passengers warned not to travel.
Sam MacDougall, operations director for Network Rail said: “Closing the line to traffic is always a last resort but it is the right thing to do to keep people safe on Tuesday given the unprecedented heatwave forecast.
“The forecast temperatures are well above those which our infrastructure is designed for, and safety must come first.”
Additional contingency support for ambulance services, such as more call handlers and extra working hours, have been put in place while the chairman of the NHS Confederation said hospitals are going to be “really, really pushed” over the next few days.
Britons are being urged to stay inside during the hottest points of the day, between 11am and 4pm, and wear sun cream, a hat, stay in the shade and keep hydrated with water.
Emergency services have also urged people to be cautious when cooling off after the body of a boy was recovered in Salford Quays, Greater Manchester, in the early hours of Sunday morning.
A search is meanwhile under way after reports of concern were made for a man seen in a river in Northumberland on Sunday.
A North East Ambulance Service spokesperson said: “We were called at 4.12pm this afternoon to reports of concerns for someone in the water off Piper Road in Ovingham.
“We currently have seven resources on scene but are currently unable to provide any further information.”
