2026 RACE BRIEFING
Chicago Marathon
+5:51 versus your goal from a single 09:00 live city forecast snapshot.
Prepare for Chicago's October marathon with seasonal context, race-day conditions and an even-pace reference for your goal time.
Explore your pace planZoom to drag the route. Keyboard: + / −, arrows, Home to reset.
2025 course reference. Check the organiser’s current course.
Race-day weather
- Air temperature
- 10°C
- Dew point
- 0°C
- Humidity
- 51%
- Rain chance
- 5%
Hover or drag to explore. Use ← → when focused.
Race day, hour by hour.
Swipe, drag or use the arrows. Select an hour for the full picture.
Forecast for 11 October 2026, America/Chicago. Open-Meteo · refreshes approximately hourly. City-level conditions; exposure varies around the course. Check the organiser for your assigned start time.
What 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 live city forecast. 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
Chicago follows a flat loop through 29 neighbourhoods, starting and finishing in Grant Park. The organiser's current course map takes precedence over the reference route.
Match the forecast to your assigned wave rather than the first start of the morning.
Check wind as well as air temperature before setting your effort for the day.
Use official course markers to assess pace when GPS readings drift around tall buildings.
What mornings like this have looked like
A useful range for planning Chicago Marathon: hourly weather near Chicago 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
- 13°C
- Humidity
- 74%
- Wind
- 16 km/h
- Hours with rain
- 18%
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
9 of 55 samples · 16%
Mean 19 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.
October conditions across all hours
October averages in Chicago, based on 2022–2024 ERA5 history. These are monthly conditions, not a race-day forecast.
Monthly, all-hours averages for Chicago, 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 ChicagoFind 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 |
Chicago Marathon FAQs
When is the 2026 Chicago Marathon?
Chicago Marathon is scheduled for 11 October 2026. Confirm the latest details on the official event website before travelling.
Is the weather shown a forecast for Chicago 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 Chicago Marathon?
At 09:00 local, the 2021–2025 ERA5 calendar-window sample near Chicago averages 13°C, 74% relative humidity and 16 km/h wind. The middle 80% of sampled start-hour temperatures is about 8–18°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 Chicago 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: 2025 reference course from RunWeather's curated catalogue. 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.