Doctors have written to the health secretary warning that last summer's deadly heatwave could be the "new normal" for NHS staff treating patients suffering from intense heat. It caused thousands of deaths, while others suffered severe dehydration, heatstroke and cardiac arrest due to the extreme temperatures. Some NHS hospitals cancelled elective surgeries in July when temperatures hit a record 104.5C (40.3C). Dr Matt Kneale, co-chair of the Medical Association of Great Britain, said: "As doctors, our guiding principle is to 'do no harm' and ignoring the impact of climate change on human health would be a direct breach of this fundamental principle of medicine." The letter was signed by Dr Matthew Lee, Head of Sustainability at the British Medical Association, Dr Amy McDonnell, Campaign Director at Zero Hour and Dr Richard Smith, Chair of the UK Health Alliance on Climate Change. The letter states: „Over 3,000 excess deaths have been recorded during these heatwaves and – as NHS staff – we have seen the effects first hand.