The hot weather has claimed the lives of hundreds people in just nine days, scientists have said.
Researchers estimated that the heatwave has led to 650 deaths in England between July 6 and 14 as the soaring temperatures show no sign of abating.
Ben Armstrong, professor in epidemiological statistics at the London School of Hygiene & Tropical Medicine, said that the hot weather could have led to the premature deaths of between 540 and 760 people.
Health officials have advised people to stay cool, drink lots of cold fluids and keep an eye on those they know to be at risk.
Professor Virginia Murray, head of extreme events and health protection at Public Health England (PHE), told The Times: “The risk of death and risk of illness really concerns us. Those with pre-existing illnesses are at much greater risk of not being able to cope with heat. It’s much harder for them to cope with cooling.”
She told the newspaper that people with breathing difficulties could find themselves struggling to get enough air to regulate their temperature. And those with heart difficulties are also more likely to suffer heart attacks, she said.
Dr Angie Bone, heatwave plan leader for PHE, said: “In this continued hot weather, it’s important to remember that high temperatures can be dangerous, especially for people who may be vulnerable such as older people, young children and those with serious illnesses.
“During very hot weather, pregnant women and people who have chronic illnesses, including cardiovascular, respiratory, renal conditions, diabetes or Parkinson’s disease, may experience discomfort if indoor temperatures are particularly hot and in using public transport.”
Prof Armstrong created the mortality statistics for the newspaper by using temperatures supplied by the Met Office and comparing it with studies he has conducted during previous heatwaves in Britain.
The news comes as the Met Office has raised heatwave alerts in more parts of Britain. South West England and the West Midlands have been elevated from level two to level three, putting the regions on a par with the South East and London.
The country experienced the hottest day of the year so far on Wednesday, with the mercury hitting 32.2C (90F).