Britain made meteorological history before noon on Tuesday, when the thermometer in Surrey recorded a provisional reading of 39.1 degrees Celsius (102.4 degrees Fahrenheit), the highest level ever recorded in the United Kingdom.

The record in Surrey, set at 10:40 a.m., was quickly surpassed. About two hours later, the Met Office, Britain’s national weather service, said the provisional temperature at Heathrow Airport had hit 40.2 Celsius (104.4 Fahrenheit). If confirmed, it would be the first time that the temperature in Britain had exceeded 40 degrees Celsius.