At Kew Gardens in Greater London last May, a thermometer climbed to 35.1°C — a number so far outside the expected range that it exceeded not only the station's own previous record of 29.3°C but the entire UK's May record of 32.8°C.

That single reading, the Met Office noted, was more typical of mid-summer than late spring. It was, in retrospect, a warning of what June would bring. June 2026 became the hottest June ever recorded in England, according to provisional Met Office data. Wales and the UK as a whole registered their second-warmest June since measurements began in 1884.

For the first time since the extreme heat warning system was introduced in 2021, a red alert was issued for three consecutive days — a threshold that signals a serious risk to life. Overnight temperatures were particularly striking: England's minimum temperatures ran 2.6°C above average, with "tropical nights" — when the thermometer never fell below 20°C — occurring with unusual frequency across the country. The heat did not arrive without context.

Five of the first six months of 2026 recorded mean temperatures at least 1°C above their long-term averages, with only January falling below the norm, according to Met Office scientist Dr Emily Carlisle.