The warning, for Thursday to Sunday, comes as the forecaster predicted 35°C in places or even an “isolated” 36°C – below last month’s record temperatures, which peaked above 40°C in some spots, but still uncomfortably hot for many people.
The vulnerable are likely to experience adverse health affects, while the wider population could also be affected, the alert said.
Delays to travel are possible and there is an increased risk of water accidents and fires as more people visit coasts and beauty spots, the Met Office also warned.
Technology has also been feeling the heat, with a spike in overheating phones, tablets and laptops reported by users, as the high ambient temperatures affect components.
The UK Health Security Agency has already issued an amber alert covering southern and central England from noon on Tuesday until 6pm on Saturday, with experts advising people to look out for those who are older or with existing health conditions, as well as young...