The Met Office has warned that people’s lives could be at risk as it indicated it is likely that a new UK record temperature could be set early next week.
Meteorologists gave an 80% chance of the mercury topping the UK’s record temperature of 38.7C (101.7F) set in Cambridge in 2019, with the current heatwave set to peak on Tuesday.
There is a 50% chance of temperatures reaching 40C somewhere in the UK, likely along the A1 corridor, with the Met Office issuing its first ever red warning for extreme heat.
The UK Health Security Agency has increased its heat health warning from level three to level four – a “national emergency”.
Level four is reached “when a heatwave is so severe and/or prolonged that its effects extend outside the health and social care system… At this level, illness and death may occur among the fit and healthy, and not just in high-risk groups,” it said.
The Met Office red warning, for Monday and Tuesday, covers an area from London up to Manchester, and up to the Vale of York.
Met Office spokesman Grahame Madge said: “If people have vulnerable relatives or neighbours, now is the time to make sure they’re putting suitable measures in place to be able to cope with the heat because if the forecast is as we think it will be in the red warning area, then people’s lives are at risk.
“This is a very serious situation.”
He said there is an 80% chance of the all-time UK temperature record being broken, and a 50% chance of temperatures of 40C being reached somewhere in the UK.
“Most likely that would be within the red warning area for extreme heat,” said Mr Madge.
“Probably the most likely areas to look at would be north of London and up to Lincolnshire, inland.
“Somewhere like Peterborough, Grantham, Sandy, Stevenage, those sorts of areas, A1 corridor.”
He said that temperatures reaching 40C would be a “historic event”.
“If we get to 40C that’s a very iconic threshold and shows that climate change is with us now,” he said.
“This is made much more likely because of climate change.”
Mike Childs, head of science, policy and research at Friends of the Earth, said: “Each year, the effects of climate breakdown are becoming more evident and more severe.
“Without meaningful Government intervention, millions of Brits, particularly older people and young children, will be at increasing risk from health-threatening heatwaves like the one we’re experiencing.”
A No 10 spokesman said railway speed restrictions may be needed on “some parts of the network next week to manage the hot weather and to avoid any potential damage”.
Downing Street said that that Cobra met on Thursday amid the heatwave, and discussions with sectors including the NHS will “continue to work closely with all of those sectors over today, through the weekend and into early next week”.
Meanwhile, motorists have been advised to try to make their journeys outside of the hottest periods of the day, particularly if they have older cars.
Sean Sidley, AA patrol of the year, said: “There are reports of road gritters being out this weekend to reduce the chances of our roads melting.
“If it does get sticky on the roads there’s nothing worse than being stuck in a jam with the mercury rising, so make sure you carry plenty of water – at least a litre per person – and sufficient fuel, or if you’re driving an electric vehicle (EV) – make sure you have plenty of charge so you can use the air-conditioning when needed.”
Tim Doran, from the RNLI Water Safety Team said the service was anticipating a “busy weekend” for its lifeboat crews and lifeguards.
“If you are planning on going to the beach, we would encourage you to visit a lifeguarded beach and swim between the red and yellow flags,” he said.