London Marathon 2025: Weather, records and event milestones

The forecast for Sunday indicates that the southeast will experience a largely settled day with bright intervals, which are expected to be prolonged in the far south and southeast. Any fog or low cloud in these areas is expected to clear quickly, resulting in a fine day with light to moderate winds.

Temperatures will vary across the country, with warm conditions in the southeast, possibly up to about 21-22°C in some areas.

These temperatures fall just slightly short of some of the highest recorded throughout the event’s history and well ahead of last year's maximum temperature at St James's Park of 12.6°C.

READ MORE: A record-breaking March for sunshine

London Marathon weather records

The London Marathon has seen a variety of weather conditions over the years, with some events seeing temperatures rising slightly over 24°C while other events have seen much colder conditions of almost -2°C. 

The highest ever recorded maximum temperature was 24.2°C at St James Park in 2018. On the opposite end of the spectrum, the lowest ever recorded minimum temperature was -1.9°C at Kew Gardens in 1991.

The most rainy day in the history of the marathon saw runners soaked by 22.6mm of rain at Greenwich in 1983. Wind conditions have also been unpredictable, with the maximum wind gust recorded as high as 35mph at Kew Gardens in 1986. On the brighter side, the brightest day in the marathon had 12.1 hours of sunshine at Kew Gardens in 1998.

Guinness World Record attempt

This year’s event is also hoping to break an impressive record. For the first time ever in the event's history, this year's event looks set to achieve the Guinness World Records title for the largest number of marathon participants.

Having more than 56,000 finishers on Sunday, April 27, the event could surpass the previous record of 55,646 finishers held by the TCS New York Marathon in November 2024.

The London Marathon itself was initially held on 29 March 1981. More than 1.3 million participants have completed the event since its inauguration, and the millionth participant crossed the line in 2016.

The London Marathon has also been a significant charity fundraising race, with more than £1.3 billion being raised for good causes. The Official Charity of the Year for this year is Pancreatic Cancer UK.

Whether running or cheering from the sidelines, it's important to dress appropriately and stay informed about weather conditions throughout the day.

Keep up to date with weather warnings, and you can find the latest forecast on our website, on YouTube, by following us on X and Facebook, as well as on our mobile app which is available for iPhone from the App store and for Android from the Google Play store.