Hospital A&E departments across Birmingham are treating hundreds more patients as a result of the heatwave, with one trust reporting an increase of more than 40 per cent.
People with asthma, respiratory problems and heart disease are flocking to Accident and Emgergency as temperatures continue to top 30?C (86?F) across the Midlands.
Doctors at City Hospital and Sand-well General Hospital have seen patient numbers increase by more than 40 per cent.
Normally medics see about 280 patients in casualty, but daily attendance figures are now close to topping 400.
A spokeswoman for Sandwell and West Birmingham Hospitals NHS Trust, which runs both sites, said: "There has been a marked increase in the numbers coming to A&E over the past fortnight, which we believe is due to this hot spell.
"Earlier this week we had 398 patients come in, which is quite a bit higher than usual. Mainly people are coming in with asthma attacks, respiratory problems and heat exhaustion."
An extra emergency GP has been brought in "on loan" from Heart of Birmingham Primary Care Trust to help staff cope with the extra cases.
University Hospital Birmingham NHS Foundation Trust - which runs the Queen Elizabeth and Selly Oak hospitals - have also seen patient numbers in casualty rise over the past fortnight. "We've seen an increase of between five to seven per cent in people coming into A&E, predominantly with bites and stings, which we're putting down to this hot weather," said a trust spokeswoman.
"It may be due to bugs not normally seen in the UK having come over so people are getting unusual reactions to these bites and stings."
A health warning has been issued across the country, particularly in urban areas, as the hot weather produces potentially dangerous levels of air pollution.
A Met Office spokesman claimed higher pollution levels are becoming an increasing danger.
"I think we will see the mortality rate in the UK rise sharply," he said.
Concentrations of gases like nitrogen dioxide, found in car fumes and industrial output, can cause breathing difficulties in vulnerable people particularly the elderly, and can exacerbate conditions such as asthma.
Andrew Kibble, an environmental scientist with Health Protection Agency in the West Midlands, said the warm weather and lack of wind means pollutants remain close to the ground, causing smog to form.
He said: "Nitrogen dioxide irritates the airways and lungs so the people who suffer most in this kind of weather are asthmatics."
He added that anyone with respiratory problems should ensure they have their medication with them.