2026 RACE BRIEFING
Chicago Half Marathon
+5:00 versus your goal from a single 09:00 five-year ERA5 calendar-window mean snapshot.
Explore the Chicago Half Marathon with race-day weather when available, course context and an even-pace reference for your goal time.
Explore your pace planThe Life Time Chicago Half Marathon uses a flat route with a traffic-restricted stretch of Lake Shore Drive. Confirm the current course map and start instructions with the organiser.
See organiser route detailsRace-day weather
This edition has already taken place.
The historical weather below is useful context for future planning. We do not substitute today’s weather for a past race.
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 Life Time Chicago Half Marathon uses a flat route with a traffic-restricted stretch of Lake Shore Drive. Confirm the current course map and start instructions with the organiser.
Check the wind forecast for the exposed Lake Shore Drive section before locking in an opening effort.
Compare the conditions at your start and expected finish before settling on kit and effort.
Confirm late changes to the route, start wave and logistics with the organiser.
What mornings like this have looked like
A useful range for planning Chicago Half 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
- 17°C
- Humidity
- 76%
- Wind
- 14 km/h
- Hours with rain
- 13%
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
10 of 55 samples · 18%
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.
September conditions across all hours
September 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 calculator1:40:00 finish · 21.1 km
View even-pace checkpoints
| Distance | Elapsed time |
|---|---|
| 5.0 km | 0:23:42 |
| 10.0 km | 0:47:24 |
| 15.0 km | 1:11:06 |
| 20.0 km | 1:34:48 |
| 21.1 km · Finish | 1:40:00 |
Chicago Half Marathon FAQs
When is the 2026 Chicago Half Marathon?
Chicago Half Marathon is scheduled for 27 September 2026. Confirm the latest details on the official event website before travelling.
Is the weather shown a forecast for Chicago Half 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 Half Marathon?
At 09:00 local, the 2021–2025 ERA5 calendar-window sample near Chicago averages 17°C, 76% relative humidity and 14 km/h wind. The middle 80% of sampled start-hour temperatures is about 13–21°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 Half 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.
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.