The short answer
London Marathon weather history from 2015 to 2024 is mostly cool. The air at the start ranged from 5.8 °C (42 °F) in 2016 to 18.9 °C (66 °F) in 2018, the hottest London Marathon on record. Eight of nine race days rated Good for a four-hour runner, with Low heat stress.
Key takeaways
- Eight of nine race days from 2015 to 2024 had Low heat stress all the way round.
- 2018 was the exception: 18.9 °C (66 °F) at the start and Moderate heat stress from the line.
- The October races of 2021 and 2022 were mild, not warm.
- Rain was light every year, at most 1.5 mm (0.06 in) for a four-hour runner.
On this page
- What does London Marathon weather history show?
- What were London Marathon temperatures by year?
- Why was 2018 so hot, and why do our numbers differ from the Met Office's?
- How does the London course change your pace?
- How warm does London get at your finish time?
- How should you plan your London race morning?
- How can you check London weather at your own pace?
- Questions runners ask
- Sources and method
Words this guide uses
- ERA5
- The Copernicus reanalysis of past weather, hourly, on a grid about 31 km (19 miles) apart.
- WBGT
- Wet-bulb globe temperature, a heat-stress number combining air temperature, humidity, sun and wind.
- Dew point
- The temperature at which the air would be saturated; above about 15 °C (59 °F), sweat evaporates noticeably less.
What does London Marathon weather history show?
London Marathon weather history shows a race that is usually cool and kind. From 2015 to 2024, eight of nine race days stayed at Low heat stress for a four-hour runner, and 2018 was the one warm exception. Our marathon weather history hub compares London with Boston, Berlin and Comrades.
The numbers are our own. We took hourly ERA5 weather at the real date and start time, then timed it to a runner along the course: a pace-timed forecast run backwards, giving the weather for each stretch of the course at the time you would have run it.
| The race at a glance | London Marathon, UK |
|---|---|
| Date | A Sunday in late April (October in 2021 and 2022) |
| Start time in our data | 10:00 (10:10 in 2019, 09:30 in 2021, 09:40 in 2022) |
| Distance | 42.2 km (26.2 miles), Blackheath to The Mall |
| Climbing | About 90 m (295 ft) up and 125 m (410 ft) down |
| Finish times on our race page | 2:30 to 6:30 |
What were London Marathon temperatures by year?
Mostly between 6 and 14 °C (43 and 57 °F) at the start, with 2018 far above the rest. The table shows each race day for a four-hour finisher, at 5:41 per km (9:09 per mile).
| Date | Start | Air at the start, °C (°F) | Warmest air, °C (°F) | Highest dew point, °C (°F) | Peak WBGT, °C (°F), level | Rain, mm (in) | Rating |
|---|---|---|---|---|---|---|---|
| 26 Apr 2015 | 10:00 | 7.8 (46) | 9.3 (49) | 6.4 (44) | 10.0 (50), Low | none | Good |
| 24 Apr 2016 | 10:00 | 5.8 (42) | 9.2 (49) | −0.2 (32) | 9.3 (49), Low | 0.1 (<0.01) | Good |
| 23 Apr 2017 | 10:00 | 9.8 (50) | 13.2 (56) | 4.9 (41) | 13.3 (56), Low | 0.5 (0.02) | Good |
| 22 Apr 2018 | 10:00 | 18.9 (66) | 21.6 (71) | 13.6 (56) | 20.6 (69), Moderate | none | Fair |
| 28 Apr 2019 | 10:10 | 10.1 (50) | 11.9 (53) | 5.3 (42) | 12.6 (55), Low | 0.7 (0.03) | Good |
| 3 Oct 2021 (autumn race) | 09:30 | 10.7 (51) | 15.2 (59) | 9.3 (49) | 15.2 (59), Low | none | Good |
| 2 Oct 2022 (autumn race) | 09:40 | 13.3 (56) | 16.4 (62) | 11.9 (53) | 17.8 (64), Low | 0.5 (0.02) | Good |
| 23 Apr 2023 | 10:00 | 11.2 (52) | 12.3 (54) | 8.4 (47) | 14.5 (58), Low | 1.5 (0.06) | Good |
| 21 Apr 2024 | 10:00 | 8.3 (47) | 10.7 (51) | 0.9 (34) | 10.6 (51), Low | 0.2 (0.01) | Good |
There was no mass race on the course in 2020. Apart from 2018, the October 2022 race was the warmest and most humid, yet it still rated Good.
Why was 2018 so hot, and why do our numbers differ from the Met Office's?
The race fell in a warm, humid spell, and the Met Office recorded 24.2 °C (76 °F) at St James's Park, the London Marathon record. Our data shows 18.9 °C (66 °F) at the start and 21.6 °C (71 °F) at the warmest for a four-hour runner.
This is reanalysis, not a thermometer at the start line. ERA5 gives hourly values on a grid about 31 km (19 miles) apart, averaging central London with greener, cooler ground. A park station's daily maximum can also come in mid-afternoon, after most runners finish. The gap runs the same way in 2024: the Met Office's St James's Park maximum was 12.6 °C (55 °F), and our warmest air for a four-hour runner was 10.7 °C (51 °F).
How does the London course change your pace?
Very little after the first few kilometres. In our course profile, the start sits about 42 m (138 ft) up near Blackheath and drops to about 8 m (26 ft) by km 6 (mile 3.7).
After that, London is nearly flat along the Thames, past the Cutty Sark, over Tower Bridge at about halfway and round Canary Wharf. On a warm day, slower runners lose more time than the leaders, Ely and colleagues (2007) found.
How warm does London get at your finish time?
A little warmer for slower runners, and noticeably warmer in the sun. On 22 April 2018, here is the same race day at three finish times.
| Finish time | Average pace | Warmest air, °C (°F) | Hottest feels like, °C (°F) | Peak WBGT, °C (°F) | Rating |
|---|---|---|---|---|---|
| 3:00 | 4:16 per km (6:52 per mile) | 21.3 (70) | 24.5 (76) | 20.6 (69) | Fair |
| 4:00 | 5:41 per km (9:09 per mile) | 21.6 (71) | 26.2 (79) | 20.6 (69) | Fair |
| 5:00 | 7:07 per km (11:27 per mile) | 21.7 (71) | 26.7 (80) | 20.6 (69) | Fair |
All three met Moderate heat stress from the start line. The feels like climbs with finish time because slower runners spend longer in the midday sun.
How should you plan your London race morning?
Plan for a cool start and keep a warm-day plan ready.
- Cool and dry (most years): an old top for the start, then race kit. Our guide to what to wear for a marathon covers it.
- Warm (as in 2018): a cap, sunscreen and a slower first half.
- Check the dew point: above 15 °C (59 °F), sweat evaporates less. See WBGT for runners for how heat stress is graded.
The American College of Sports Medicine (2007) warns that heat illness can strike even when it's relatively cool. Official race flags and medical advice override this article, which is not medical advice.
How can you check London weather at your own pace?
Open the London race page, pick a year and set your finish time. It shows the air, feels like, dew point and heat stress you'd have met at the Cutty Sark, Tower Bridge, Canary Wharf and The Mall. In race week, our guide to the race day weather forecast shows how to read the forecast kilometre by kilometre.
Questions runners ask
What was the hottest London Marathon?
2018. The Met Office recorded 24.2 °C (76 °F) at St James's Park on race day, the highest in London Marathon history. Our ERA5 data puts the start at 18.9 °C (66 °F) and the warmest air a four-hour runner met at 21.6 °C (71 °F), with Moderate heat stress from the start line. The previous record, 22.7 °C (73 °F) in 1996, was also at St James's Park.
What was the coldest London Marathon?
On Met Office records, 1991, when Kew Gardens fell to −1.9 °C (29 °F). In our 2015–2024 data, the coolest race day was 2016: 5.8 °C (42 °F) at the start, a dew point near 0 °C (32 °F) and a feels like as low as 1.4 °C (35 °F) for a four-hour runner. Dry, cold air like that suits fast running once you're warm.
Why were the 2021 and 2022 London Marathons held in October?
After 2020's race became an elite-only event on laps of St James's Park, the mass race returned on 3 October 2021, and 2 October 2022 followed before April returned in 2023. In our data both were mild: the warmest air for a four-hour runner was 15.2 °C (59 °F) in 2021 and 16.4 °C (62 °F) in 2022. Both rated Good.
Does it usually rain at the London Marathon?
Not much. In our 2015–2024 data, the wettest race day was 2023, with 1.5 mm (0.06 in) for a four-hour runner, and three race days were dry. The Met Office's wettest London Marathon was 1983, with 22.6 mm (0.89 in) at Greenwich. Light rain on a cool day is mostly a kit question: a cap and a throwaway layer help.
Do you need a throwaway layer at the London Marathon start?
Often, yes. The air at the start averaged 10.7 °C (51 °F) in our data, and was below 10 °C (50 °F) in four of nine years. Standing still at that temperature feels cold, even though it's ideal once you're running. An old top you can drop at the start keeps you warm without overheating later. Check the forecast in race week to decide.
Your race, at your pace.
Pick Comrades, Berlin, London or Boston, set your finish time, and see the heat stress, feels like and dew point you’d have met at every landmark, on every race day from 2015 to 2024.
Sources and method
- Copernicus Climate Change Service (ECMWF) (2023). ERA5 hourly data on single levels from 1940 to present
- Met Office (2025). London Marathon 2025: weather, records and event milestones
- Met Office (2018). Warm and humid marathon weekend ahead
- Medicine and Science in Sports and Exercise (2007). Impact of weather on marathon-running performance (Ely, Cheuvront, Roberts and Montain)
- American College of Sports Medicine (2007). Position stand: exertional heat illness during training and competition (Armstrong et al.)
Every London Marathon mass race from 2015 to 2024 (2020 was an elite-only race on laps of St James's Park and is left out; 2021 and 2022 ran in October), at the real date and start time: 10:00, except 10:10 in 2019, 09:30 in 2021 and 09:40 in 2022. Weather is hourly ERA5 reanalysis (Copernicus Climate Change Service, ECMWF) at the two 0.25° grid points the course crosses; each stretch takes its nearest point. The RunFast engine times a runner along our 42.2 km course model at an even effort for a 3:00, 4:00 or 5:00 finish, with pace adjusted for gradient, and reads the air, dew point, feels like at running pace, WBGT (Liljegren et al., 2008, with cloud worked back from ERA5 sunshine) and rain at each stretch when the runner is there. WBGT levels: Low below 18.3 °C (65 °F), Moderate to 22.8 °C (73 °F), High to 27.8 °C (82 °F), Extreme above. Ratings: Fair at Moderate heat stress, Tough at High or Extreme, or in cold rain. Climbing is measured from the course profile, counting rises of 3 m (10 ft) or more. Station records are quoted from the Met Office. Fahrenheit and inch values are our conversions. RunFast is independent of the London Marathon's organisers.
Wes Thomson
Wes Thomson builds RunFast, which times the heat, humidity and dew point to a runner's own pace along the route, and its sister Windline, live wind forecasts for cyclists. Both run on the same forecast engine. He writes these guides with one focus: what the weather will do to your run, kilometre by kilometre, and how to plan around it.