Ministers will hold an emergency Cobra meeting on Saturday after meteorologists warned of record high temperatures in England that could put lives at risk.
Cabinet Office minister Kit Malthouse is to chair a meeting of the Government’s Cobra civil contingencies committee to discuss the escalating heatwave, a Government spokesman said.
It will be the second Cobra meeting Mr Malthouse has led on the issue.
Meteorologists have given an 80% chance of the mercury topping the UK’s record temperature of 38.7C set in Cambridge in 2019, with the current heatwave set to peak on Tuesday.
Temperatures will climb over the weekend, and the Met Office has issued an amber warning for heat covering much of England and Wales from Sunday until Tuesday.
Daytime temperatures on Saturday are predicted to be around 27C in London, 26C in Cardiff, 23C in Belfast and 21C in Edinburgh.
On Sunday, it could reach 30C in the capital, 27C in Cardiff, 24C in Belfast and 23C in Edinburgh.
Temperatures are forecast to increase by several more degrees on Tuesday – up to the mid-30s for much of England and Wales.
There is a 50% chance of temperatures reaching 40C somewhere in the UK, likely along the A1 corridor which runs from London to Scotland through counties including Lincolnshire, Nottinghamshire, Yorkshire and the North East, 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.
A 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.”