Chicago Marathon

This edition is listed as Marathon in Chicago, Illinois, USA.

When we have race morning history, use that range for planning, not as a promise. Inside about 14 days, the live forecast on this page is the better read. We do not invent a start-hour number when history is not loaded here.

2021 (10 Oct 2021) was the hottest Chicago Marathon morning in that set, WBGT around 16°C. Treat that year as the spike, not as the usual morning.

2021 (10 Oct 2021) was the windiest Chicago Marathon morning in that set, around 25 km/h. Wind still changes what the same pace costs. Treat that year as the spike, not as the usual morning.

Inside about 14 days, use the live forecast on this page. The current outlook is about 19°C to 23°C, around 9 km/h wind and 58% humidity. Forecasts move. Further out, use race morning history, not a locked plan.

Heat, humidity, wind or a lumpier day than you hoped all raise the chance of a late fade. If the start feels easy, don't spend it. Back off early, and hold even effort even if that means slower than the A-goal. The preview on this page is the starting point. Full personalised splits sit in Race Pass or Pro.

About 33 m of climbing and 32 m of descent. Mostly flat. Almost all of it sits within 2%. No steep grades over 6%. No counted climbs.

It is an estimate of how the course and conditions could move your baseline. Your body still decides the rest: heat adaptation, fuelling, prep, mindset, how you race, and whether you can draft.

The free page covers conditions, course context and a finish preview. Full personalised pacing and weather-adjusted splits sit in Race Pass or Pro.