Temperatures on Monday will be hotter than in Spain, France, Italy, Malta and the Balearic Islands, as a 1,000-mile heat bubble chokes the country.
Parts of Britain could overshadow notorious hot spots like Seville, Spain and the south of France, experts say.
A ‘pool’ of intense heat will engulf the UK at the start of the week as weather models predict air temperatures of 42C and ground temperatures of 45C.
Jim Dale, meteorologist for British Weather Services, said: “This is a heat bath and resembles an Arctic cold pool we sometimes see in winter.
“It’s a liquid heat bubble that, when it moves across the UK, can push the temperature in isolated areas higher than anywhere else in Europe.
“It’s not entirely out of the question that the UK could see a window into the intensely hot period when temperatures are the highest in Europe.”
Seville is expected to hit 41C next week, while Malta floats in the low-30Cs, Nice, in France, hits 32C and Ibiza 32C.
Even Morocco, in North Africa, will be cooler than the UK at 32C, while Bangkok, Thailand, will linger at a relatively cold 33C.
The extreme heat has prompted warnings not to ‘play in the sun’ and brace for power cuts, travel chaos, water shortages and mobile phone outages.
Nighttime temperatures will hover above 20C at the start of the week, while Britain is sweltering in unbearable ‘tropical nights’.
Government officials have issued a series of warnings as the UK boils in extreme temperatures, even for desert climates.
Healthy adults, along with the elderly and frail, are warned to stay out of the sun to avoid the risk of fatal heat stroke.
Met Office chief executive Penny Endersby said: “I can say that the extreme heat that we are now forecasting is unprecedented.”
“In the UK we are used to treating a hot spell as an opportunity to play in the sun.”
“This is not that kind of weather.”
“Our lifestyle and our infrastructure are not adapted to what is to come.”
A plume of toasty air will feed Britain between high pressure over land and low pressure to the west.
The two systems will act as a funnel and allow an air channel to flow across the continent from North Africa.
Britons are being warned not to underestimate the deadly threat of heat never before experienced in the UK.
Dale said: “There is now every possibility of reaching 40°C on Monday and Tuesday, and there is absolutely no doubt about it – these temperatures can and will be deadly.”
“This hot plume comes from North Africa after traveling through Spain and France towards the end of the weekend.”
It is the first time the Met Office has issued a red ‘extreme heat’ weather warning, which will remain in effect in southeastern and central England Monday and Tuesday.
At the beginning of next week, a less strict orange warning was issued in the rest of the country.
A separate ‘national emergency’ level 4 heat health warning warns of deadly heat wave conditions until mid-week.
Meteorologist Paul Gundersen, chief of the Met Office, said: “Exceptional, perhaps record-breaking temperatures are likely to be early next week, quite far over the red warning zone on Monday, and a little more east and north on Tuesday.”
“There is a 50 percent chance that we will be able to see temperatures above 40°C and an 80 percent chance that we will see a new maximum temperature reach.”
Health risks will be exacerbated by record temperatures at night making it impossible to get a reprieve.
Brits are urged to rethink daily activities to avoid exertion and deadly overheating.
Mr Gundersen said: “The nights are also likely to be exceptionally warm, especially in urban areas.”
“It’s important that people plan for the heat and consider changing their routines.”
“This level of heat can have adverse health effects.”
Meteorologist Alex Deakin said temperatures will soar below 30 degrees on Sunday before reaching 40 degrees next week.
Britain faces ‘serious’ problems as temperatures skyrocket to levels never seen before in the UK, he warned.
He said: “We have issued our first-ever red extreme heat warning.”
“We are particularly concerned about the temperatures rising early next week – unprecedented temperatures.”
“We are looking forward to a temperature of 40 °C, there is a good chance that we will beat the temperature records.”
“This heat builds up and is going to cause serious problems.”