According to PA, the alert has been issued for all but one region, with some areas being warned of the potential for “significant impacts” on the health and social care sector.
The alert from the UK Health Security Agency (UKHSA) and Met Office will come into force from Monday morning and remain in place until Thursday afternoon.
Temperatures are expected to reach highs of 30C, particularly in the South East, with the strongest warnings issued for that region, the East Midlands, the east of England and East Anglia.
The only region not covered is the North East.
The UKHSA has warned of an “increase in risk of mortality amongst vulnerable individuals and increased potential for indoor environments to become very warm” for the north-west and north-east of England, the west of England, the South West and London.
Liam Esslick, a meteorologist at the Met Office, said: “According to the latest models, there is a chance temperatures could reach 30C. It’s not guaranteed but this will likely be towards the south-east of England, particularly London, Essex and Kent.
“My advice to people would be by all means go out and enjoy. They have been waiting for summer.
“But UV levels are going to be high and the sun will be very intense. Wear protection like sun cream, stay hydrated and try to get some shade in the midday sun.
“People sensitive to the sun should take particular precautions.”
Mr Esslick added that the longer-term weather forecast remains uncertain, with a “breakdown” expected from late Wednesday into Thursday.
He said: “It could be a little thundery with a breakdown towards the back end of the week.
“But Monday, Tuesday and Wednesday are looking fine.”
