The UK is set for another day of scorching heatwave conditions, with temperatures in some areas not dipping below 24C overnight.
Monday was the hottest day of 2018 so far, with the Met Office recording 33.3C in Santon Downham in Suffolk.
But the heat is not due to reach its peak until Thursday or Friday.
A level three heat health watch alert is still in place for much of the east and south-east of England.
The public are being advised to take shelter from the sun, as the joint warning from the NHS, Public Health England and the Met Office says there is a 90% probability of heatwave conditions until 09:00 BST on Friday.
The Met Office expects temperatures to remain in the low 30s throughout Tuesday, climbing to a likely 33C on Wednesday, while Thursday and Friday could see 34C.
It says temperatures above 34C “can’t be ruled out”.
The hottest July day on record in the UK was July 1 2015, when the mercury hit 36.7C at Heathrow.
Several places in England have gone without significant rainfall for 54 consecutive days.
The longest run with no rain at all this summer is 48 days at Brooms Barn, near Bury St Edmunds.
A Met Office spokesman said: “It’s the driest first half of the summer since 1961.
“For the UK as a whole, we’ve only seen about 20% of the rainfall we’d normally expect throughout the whole summer. Parts of southern England have seen only 6%.”
The dry spell has led to a hosepipe ban, closed canals and revealed ancient hidden landscapes.
The National Farmers’ Union has warned of crops “parched to the bone” and livestock farmers resorting to using winter rations, as grass has stopped growing.
The NHS says the hot weather could increase risks to vulnerable patients, such as older people, babies and young children, and people with serious chronic conditions.