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Live forecasts update automatically; written guidance last reviewed 16 June 2026 by the Story Native weather desk. Data from national met services via Open-Meteo.
A London heat wave is defined by the Met Office as three or more consecutive days when the daily maximum temperature reaches at least 28°C. The most extreme event on record occurred in July 2022, when the capital exceeded 40°C for the first time, prompting a rare red warning.
What qualifies as a London heat wave?
For the London area, the Met Office uses a regional threshold of 28°C for three days running. This is slightly lower than the general UK heatwave threshold for parts of southern England (27°C) because London’s urban heat island effect often makes it a few degrees warmer than surrounding areas. A heatwave can occur at any point from June to August, though the highest temperatures typically arrive in mid-July.
How to stay safe during a London heat wave
During a heatwave, the key risks are dehydration, heat exhaustion, and heatstroke. Stay indoors between 11am and 3pm, keep curtains closed, and drink plenty of water. Check on elderly neighbours and avoid leaving children or pets in parked cars. The NHS advises to cool your skin with a damp cloth or fan, and to avoid strenuous exercise until the heat subsides. For real-time conditions, check the UK weather hub or the 10 day weather forecast UK.
How long does a London heat wave usually last?
Most London heatwaves last between three and seven days. Prolonged events, like the 10-day spell in August 2020, are rarer. The Met Office issues warnings when conditions persist beyond three days.
What is the difference between a heat wave and a UK heatwave?
A UK heatwave uses regional thresholds (27–28°C) across the whole country, while a London heat wave applies the same definition but specifically to the capital’s weather stations. Both require three consecutive days above the threshold.
Is there a heat in London today?
Check the Met Office’s latest warnings for current conditions. During a London heat wave, daytime temperatures often exceed 30°C, with night-time minima rarely dropping below 18°C. View the latest UK weather hub for up-to-date forecasts.