2027 RACE BRIEFING
London Marathon
+0:00 versus your goal from a single 09:00 five-year ERA5 calendar-window mean snapshot.
Plan for the 2027 London Marathon's two-day edition with historical April conditions and a clear distinction between climate and race-day forecasts.
Explore your pace planZoom to drag the route. Keyboard: + / −, arrows, Home to reset.
Route edition unverified. Check the organiser’s current course.
Race-day weather
Good preparation starts before the forecast.
Race-day forecasts appear here within 15 days of the event, when data is available. Until then, explore the course and historical weather below.
Explore historical weatherWhat the weather may cost
RunWeather’s shared pace model estimates the effect of one weather hour at your goal effort. It is a planning preview, not a predicted finish time or a full course simulation.
Snapshot at 09:00 local using five-year ERA5 calendar-window mean. Route climbing, turns, shelter, fuelling, fitness, heat adaptation and wave timing are not modelled here. Rain is excluded because a probability is not a measured rain rate. Explore the pace model.
What the course asks of you
The 2027 event takes place on 24 and 25 April, with both days following the route from Greenwich to Westminster. Check your allocated race day before planning travel or weather.
- Elevation
- 40 m
Hover or drag to explore. Use ← → when focused.
Use your allocated Saturday or Sunday race date; the two days can have different weather.
Choose your kit from the forecast during your own start and finish window.
Use the official course map for current route details; the reference geometry does not identify an edition.
What mornings like this have looked like
A useful range for planning London Marathon: hourly weather near London for the same calendar date ±5 days in 2021–2025. These are city-grid samples, not past race editions or a forecast.
The five-year picture
- Air temperature
- 9°C
- Humidity
- 79%
- Wind
- 14 km/h
- Hours with rain
- 11%
Hover or drag to explore. Use ← → when focused. Shading: middle 80% of sampled temperatures.
The sampled air warms by about 4°C across four hours. Check your expected finish-hour forecast, not just the start.
Where the breeze came from
20 of 55 samples · 36%
Mean 16 km/h
The petals show how often the wind came from each direction at the sampled start hour. They do not predict the direction on race day.
A city-point wind rose cannot tell you which parts of the course will be sheltered or exposed. Use the live forecast and the organiser’s route map together.
Method: 55 ERA5 hourly samples at 09:00 local time, across 11 calendar days per year in 2021–2025. A 09:00 sample is used because the organiser has not confirmed a first start in this guide. Grid weather is modelled reanalysis, not an on-course station reading. Open-Meteo Historical Weather API . Snapshot generated 2026-09-29.
April conditions across all hours
April averages in London, based on 2022–2024 ERA5 history. These are monthly conditions, not a race-day forecast.
Monthly, all-hours averages for London, 2022–2024. Not past race-day measurements or a forecast. Rain is the share of historical hours with precipitation, not the chance of rain on race day. Source: Open-Meteo ERA5.
Explore running weather in LondonFind your starting pace
Start with your goal. Leave room for the day.
Set a finish time to compare an even-pace baseline with a one-hour weather snapshot. Use the changing forecast and course notes to decide where to be more conservative.
The baseline ignores hills and stops. The weather preview models one selected hour.
Explore the heat pace calculator3:15:00 finish · 42.2 km
View even-pace checkpoints
| Distance | Elapsed time |
|---|---|
| 5.0 km | 0:23:06 |
| 10.0 km | 0:46:13 |
| 15.0 km | 1:09:19 |
| 20.0 km | 1:32:26 |
| 25.0 km | 1:55:32 |
| 30.0 km | 2:18:39 |
| 35.0 km | 2:41:45 |
| 40.0 km | 3:04:51 |
| 42.2 km · Finish | 3:15:00 |
London Marathon FAQs
When is the 2027 London Marathon?
The 2027 London Marathon takes place on Saturday 24 and Sunday 25 April. Check the race day allocated by the organiser; the weather may differ between days.
Is the weather shown a forecast for London Marathon?
The race-day forecast panel uses provider data for the event date when available. The 2021–2025 ERA5 race-window sample describes nearby calendar dates, not held race editions or a prediction for race day. Monthly averages, when shown, cover all hours of the event month.
What is the historical race-window weather like for London Marathon?
At 09:00 local, the 2021–2025 ERA5 calendar-window sample near London averages 9°C, 79% relative humidity and 14 km/h wind. The middle 80% of sampled start-hour temperatures is about 7–12°C. These are 55 city-grid samples from the event date ±5 days, not observations from held editions or a forecast.
Can the race-window history predict London Marathon weather?
No. It describes the same calendar window in 2021–2025. Use the live event-day forecast when available, check conditions through your own expected finish time, and follow the organiser for current start and course information.
Sources & race information
Weather-window data: Open-Meteo ERA5 Historical Weather API, sampled at the city grid for 2021–2025 and generated 2026-09-29. These calendar-window samples are not official race-day observations.
Guide reviewed . RunWeather is an independent guide, not the race organiser. Dates, waves and routes can change; the organiser’s latest instructions take priority. Course reference: Reference course from RunWeather's curated catalogue; edition unverified. The next edition may differ; elevation is approximate.
Keep exploring
A race plan that goes with you.
Explore race planning and running forecasts in RunWeather. Keep your training and race-day preparation together.