Early July saw Britain basking in a brief heatwave, with air temperatures across much of south and east England hitting the mid 30s centigrade. On July 1, the Met Office announced that the UK had recorded the hottest July day on record, with temperatures hitting 36.7° centigrade at Heathrow airport. The claim was widely repeated in the media—the BBC’s headline read “Hottest July day ever recorded in UK”, while The Guardian opted for a live blog under the headline “Heatwave live: Britain swelters on hottest July day on record”. But eagle-eyed climate bloggers immediately spotted a problem with the so-called...