The second amber heat health alert in two weeks is set to come into force on Friday, as temperatures are again set to pass 30C this weekend.
The alert, which covers London, the East Midlands, South East, South West and East of England, starts at midday on Friday and will last until 6pm on Tuesday.
The UK Health Security Agency (UKHSA) also issued a yellow alert for Yorkshire and Humber and the West Midlands for the same time period, with the agency warning of significant impacts across health and social care services.
It comes as temperatures could reach 28C on Friday in central and southern England, before rising to 30C on Saturday, then a potential 31C on Sunday, before peaking between 32C and 34C on Monday, the Met Office said.
An amber alert was previously issued for all regions in England on June 19, the first time it had been used since September 2023.
On the same day, temperatures reached 32.2C in Kew, west London, before heatwaves were declared across England and Wales.
An official heatwave is recorded when areas reach a certain temperature for three consecutive days, with thresholds varying from 25C to 28C in different parts of the UK.
Dr Agostinho Sousa, head of extreme events and health protection at the UKHSA, said: “We have already seen a spell of hot weather last week and temperatures are once again set to increase in the coming days, with central, southern and eastern areas of the country likely to see the biggest impacts.
“Our findings show that heat, especially at the sort of temperatures we are likely to see at the beginning of next week, can result in serious health outcomes across the population, especially for older adults or those with pre-existing health conditions.
“It is, therefore, important to check on friends, family and neighbours who are more vulnerable and to take sensible precautions while enjoying the sun.”
Met Office meteorologist Craig Snell said: “From Friday onwards we’re starting to once again see the heat build across England and Wales.
“Scotland and Northern Ireland are going to have a slightly different few days, some parts of western Scotland could see some heavy rain, especially on Friday, and we could potentially see some further rain towards the end of the weekend.
“On Friday, we’re likely to see temperatures potentially peak around 27C or 28C in central and southern parts of England, it’s going to feel quite humid.
“On Saturday, the hottest weather will be in the south east, potentially 30C.
“On Sunday, we’re most likely to see somewhere around 30C or 31C.
“It looks like the peak of the hot spell will be Monday, at the moment it’s looking between 32C and 34C, there’s a chance it’ll be hotter than the previous (heatwave).
“Tuesday, some fresher air is going to spread across the country, but we’re potentially likely to see between 31C and 33C.”
Some parts of central and southern England might meet the heatwave criteria by Monday, Mr Snell added.
As of Monday, some potential thunderstorms could move in, but it is too early to say where they might be, he said.
Temperatures are likely to go back down to the mid-20s after Tuesday, which is still above average for the time of year, the forecaster said.
