Britain could see its hottest day ever recorded during the heatwave this week, according to the Met Office.
Temperatures are predicted to rise to 37C on Thursday as children enjoy the start of the school summer holidays.
Forecasters said the July record of 36.7C could be beaten and that the all-time record of 38.5C, set in Faversham in August 2003, was also “under threat”.
However the soaring temperatures – caused by the jet stream pushing hot air up from southern Europe – will pose a health risk to vulnerable groups, such as older people and infants.
Public Health England has already issued an amber heat-health warning – one level below a “national emergency” red warning.
“Our advice to the public is to think now about anyone you know who may feel the ill-effects of hot weather – older people, those with heart and lung conditions and young children – and consider what help they may need,” said a spokesperson.
Official statistics showed there were nearly 700 more recorded deaths than average during the 15-day peak heatwave in June and July last year.
England’s chief nurse also urged people to check on their neighbours, while Asthma UK urged sufferers to keep up their medication.
Ruth May, chief nursing officer for England, said: “Like lots of people I’m looking forward to having fun in the sun with family and friends this weekend, but nobody wants to spend a pleasant day stuck in a hospital or urgent treatment centre.
“It’s really important to take simple precautions like drinking plenty of water, using high-factor sunscreen and remembering to take allergy medication if you need it – as is making sure to check in on neighbours and loved ones who can suffer the most from heat and pollen.”
Nicola Maxey, a Met Office spokesperson, said the high humidity and warm nights will play a part in increasing the health risk, as there will be little break from the heat for people who suffer from long-term illnesses, such as breathing and heart conditions.
Where is the hot weather coming from? Find out below 👇 pic.twitter.com/XtHf2xroEP— Met Office (@metoffice)July 22, 2019
“There’s some uncertainty though on just how long the heatwave conditions will last for,” the forecaster added. “It looks most likely that, at least by Saturday, most areas will see a bit of a drop in temperatures.
“There’s still a lot of sunshine around for the weekend and temperatures probably look to be not quite as hot, but with a summery feel staying for the weekend.”
Chief meteorologist Paul Gundersen also said that the high temperatures would bring the “possibility of records being broken for not only July but also all-time records.”
For the majority of the UK, temperatures need to rise to 25C for three consecutive days to be classed as a heatwave.
Public Health England has advised people to stay out of the sun, stay hydrated and keep their homes cool by shading windows in the event of extreme heat.
Agencies contributed to this report