Weather
Climate Avg| Time | Temp | Dew Pt | Humidity | Wind | Conditions |
|---|---|---|---|---|---|
| Start | 41.3 – 52.8°F | 39° Crisp | 65 – 80% | 8 mph SW | Clear sky |
| 8:00 AM | 42.4 – 54.2°F | 40° Ideal | 67 – 79% | 7 mph SW | Clear sky |
| 9:00 AM | 46.8 – 59.7°F | 45° Ideal | 59 – 76% | 6 mph SW | Clear sky |
| 10:00 AM | 52.4 – 66°F | 45° Ideal | 50 – 64% | 7 mph SW | Clear sky |
| 11:00 AM | 57.2 – 72.3°F | 45° Ideal | 43 – 61% | 9 mph SW | Partly cloudy |
| Finish | 58.8 – 76.8°F | 44° Ideal | 36 – 58% | 9 mph SW | Partly cloudy |
Based on 3-year average for this date. Real forecast available in 71 days.
Elevation Profile
Course Stats
Course Breakdown
The Loop
The flattest start in major marathoning. Don't mistake the ease for fitness. Run your plan.
You start and finish in Grant Park, heading north through downtown on Columbus Drive and LaSalle Street. The buildings channel crowd noise and create a fast-feeling atmosphere. It's a 40,000-runner field, so expect first-mile congestion.
South Side
These miles should feel comfortable. If they don't, your goal time may be too aggressive.
The course turns south through Pilsen and Chinatown. Crowds thin slightly in the residential stretches but the aid stations are well-placed. This is your reality check: halfway in, and you should feel like you're cruising.
The West Side
The quietest stretch. Stay mentally engaged and stick to your pace band.
Through Little Italy and the West Loop, these are the loneliest miles on the course. Some runners call them the forgotten miles. The scenery changes but the terrain doesn't. Focus on hydration, form, and staying on pace.
Home Stretch
Back downtown with growing crowds. On a flat course, the finish is all about managing fatigue.
You head east back toward the lakefront and Michigan Avenue. The crowds build as you return to downtown. The final two miles along Michigan Ave and into Grant Park are a straight shot to the finish. On a flat course, this is where discipline pays off.
Mile Splits
| Mile | Grade |
|---|---|
| 1 | -0.1% |
| 2 | +0.0% |
| 3 | +0.0% |
| 4 | +0.0% |
| 5 | -0.1% |
| 6 | +0.2% |
| 7 | +0.0% |
| 8 | +0.0% |
| 9 | +0.0% |
| 10 | -0.1% |
| 11 | +0.0% |
| 12 | +0.0% |
| 13 | +0.0% |
| 14 | +0.0% |
| 15 | +0.0% |
| 16 | +0.0% |
| 17 | +0.0% |
| 18 | +0.0% |
| 19 | +0.0% |
| 20 | +0.0% |
| 21 | +0.0% |
| 22 | +0.0% |
| 23 | +0.0% |
| 24 | +0.0% |
| 25 | +0.0% |
| 26 | +0.0% |
| 27 | +0.0% |
RM Difficulty Index
Race-Day Weather History
Race-morning conditions on this date over the past 9 years: median 59°F with a 54°F dew point and 10 mph wind. 3 of 9 years were warm enough to slow race pace.
| Year | Temp | Dew Pt | Wind | Rain | Sky |
|---|---|---|---|---|---|
| 2025 | 59°F | 50°F | 6 mph | — | Clear |
| 2024 | 58°F | 44°F | 8 mph | — | Clear |
| 2023 | 46°F | 38°F | 6 mph | — | Clear |
| 2022 | 59°F | 45°F | 13 mph | — | Drizzle |
| 2021 | 72°F | 66°F | 13 mph | — | Partly cloudy |
| 2020 | 59°F | 56°F | 9 mph | — | Drizzle |
| 2019 | 66°F | 63°F | 14 mph | 0.37" | Rain |
| 2017 | 58°F | 54°F | 16 mph | 0.1" | Rain |
| 2016 | 60°F | 54°F | 10 mph | — | Partly cloudy |
Morning conditions (race window) on the Chicago Marathon calendar date each year, from the ERA5 reanalysis archive — the race’s usual slot, not necessarily each edition’s exact day.
Chicago Marathon Pace Calculator & Race Plan
Chicago is about as flat as a marathon gets. Six meters of elevation gain total. If you're chasing a PR or a BQ, this is the course to do it on. The challenge here isn't the terrain, it's the weather. October in Chicago can be anywhere from perfect 50-degree running weather to an unseasonably warm 75 degrees that adds minutes to your finish.
Our model focuses on what actually matters here: weather impact and fatigue management. On a flat course, the pacing difference between a smart race and a blown-up race comes down to how well you manage the second half. The splits account for natural positive drift, heat stress if the forecast is warm, and first-mile congestion in a field of 40,000+.
Chicago Marathon FAQ
When is the next Chicago Marathon?›
The next Chicago Marathon is on Sunday, October 11, 2026.
How long is the Chicago Marathon?›
The Chicago Marathon is 26.2 miles (42.195 km), the standard marathon distance. It runs in Chicago, IL.
How much elevation gain does the Chicago Marathon have?›
The Chicago Marathon has about 19 ft (6 m) of climbing and 26 ft of descent, with a maximum grade of 1.3%.
Is the Chicago Marathon flat, downhill, or hilly?›
The Chicago Marathon starts and finishes at roughly the same elevation (net -2 m). With 19 ft of total climbing along the way, it's a fast, flat course.
How hard is the Chicago Marathon?›
Runner's Math scores the Chicago Marathon 22/100 (Moderate) — #36 of 38 marathon courses in our library, ranked by modeled time cost. The profile costs about 0:01 versus a flat course for a runner at 4:00-marathon pace.
What's the weather usually like at the Chicago Marathon?›
Over the past 9 years on this date, median race-morning conditions were 59°F with a 54°F dew point and 10 mph wind. 3 of 9 years were warm enough to slow race pace.