Parts of the UK could reach a sweltering 33C (91.4F) today, hotter than some of Europe’s top holiday destinations as well as Istanbul, Turkey which is forecasted temperatures for 30C.
It comes after the Met Office issued a new-style extreme heat weather warning and told people to watch out for sunburn and heat exhaustion.
The amber warning covers large parts of Wales, all of south-west England and parts of southern and central England.
It will be in place until Thursday, when temperatures are expected to peak.
Public Health England has also issued a heat-health alert, which will remain in place until Friday.
It advises staying out of the sun between 11:00 BST and 15:00 BST, drinking plenty of fluids and avoiding excess alcohol and physical exertion during the hottest parts of the day.
The Met Office is warning that over the next few days many people could be at risk of sunburn or heat exhaustion, including dehydration, nausea and fatigue.
The more vulnerable are being warned of more adverse health effects.