Chicago Marathon weather

Race-day forecast

October 10 in past years

At the start, 7 AM to 12 PM local time. “Heat” is the typical slowdown at the same effort, from temperature plus dew point. From Open-Meteo’s historical weather (ERA5).

About the course

A flat loop that starts and finishes in Grant Park, heading north to Wrigleyville, then west and south through the neighbourhoods. It’s one of the fastest courses in the world when it’s cool; early October can also bring warm, humid days, and wind off the lake funnels between the buildings. The race starts at 7:30 AM. Official site: chicagomarathon.com.

Your own runs, any day

Open a route in Route Forecast and choose Run for the weather along it at your pace, what to wear, and on warm days how much the heat will slow you. Open a route · Heat pace calculator · What to wear running

Questions

What’s the weather forecast for the Chicago Marathon?

The race-day forecast for the course appears on this page from about 16 days before the race, with the temperature at the start and along the course, dew point, how much the heat is likely to slow you, wind and rain. Until then the page shows the weather on October 10 in each of the past ten years.

What is the weather usually like at the Chicago Marathon?

See the table on this page: the temperature at the start, the high, dew point, wind and rain on October 10 for each of the last ten years, with the typical, coldest and warmest starts.

What should I wear for the Chicago Marathon?

Dress for about 15–20°F warmer than the forecast once you’re racing, and bring throwaway layers for the wait at the start. From 16 days out this page lists what to wear for the forecast; the what-to-wear-running calculator covers any conditions.