On 19 July 2022 the temperature at Coningsby in Lincolnshire reached 40.3 °C, the first time anywhere in Britain had recorded 40 degrees. The old record fell by 1.6 °C, an enormous margin, and dozens of stations beat it on the same afternoon.
What made it deadly was the night. London never dropped below about 21 °C, denying bodies the chance to cool. The very old and the chronically ill cannot shed that heat, and the summer's hot spells caused roughly 3,000 excess deaths, a silent disaster that shows up in mortality statistics rather than on the street.
By world standards 40 degrees is unremarkable; Phoenix would call it Tuesday. What made it a British catastrophe is that homes, railways and hospitals here are engineered for a cool maritime climate. Severity is relative, a heatwave is a hazard measured against the place it lands on.