Weather
Climate Avg| Time | Temp | Dew Pt | Humidity | Wind | Conditions |
|---|---|---|---|---|---|
| Start | 62.5 – 64.3°F | 58° OK | 72 – 93% | 10 mph SE | Partly cloudy |
| 8:00 AM | 62.6 – 65°F | 58° OK | 75 – 95% | 11 mph SE | Clear sky |
| Finish | 62.6 – 65.4°F | 60° Sticky | 79 – 96% | 11 mph SE | Clear sky |
Based on 3-year average for this date. Real forecast available in 57 days.
Elevation Profile
Course Stats
Mile Splits
| Mile | Grade |
|---|---|
| 1 | +0.0% |
| 2 | -0.2% |
| 3 | +0.1% |
| 4 | +0.0% |
| 5 | +0.0% |
| 6 | -0.2% |
| 7 | +0.0% |
| 8 | +0.0% |
| 9 | +0.3% |
| 10 | -0.1% |
| 11 | +0.0% |
| 12 | +0.2% |
| 13 | -0.2% |
| 14 | +0.2% |
RM Difficulty Index
Race-Day Weather History
Race-morning conditions on this date over the past 10 years: median 65°F with a 53°F dew point and 12 mph wind. 6 of 10 years were warm enough to slow race pace.
| Year | Temp | Dew Pt | Wind | Rain | Sky |
|---|---|---|---|---|---|
| 2025 | 66°F | 55°F | 4 mph | — | Clear |
| 2024 | 65°F | 59°F | 18 mph | — | Partly cloudy |
| 2023 | 63°F | 61°F | 9 mph | 0.19" | Rain |
| 2022 | 50°F | 38°F | 11 mph | — | Drizzle |
| 2021 | 70°F | 56°F | 14 mph | — | Clear |
| 2020 | 69°F | 61°F | 12 mph | — | Partly cloudy |
| 2019 | 65°F | 44°F | 16 mph | — | Partly cloudy |
| 2018 | 55°F | 44°F | 6 mph | — | Clear |
| 2017 | 65°F | 51°F | 11 mph | — | Partly cloudy |
| 2016 | 58°F | 45°F | 14 mph | — | Clear |
Morning conditions (race window) on the Chicago Half Marathon calendar date each year, from the ERA5 reanalysis archive — the race’s usual slot, not necessarily each edition’s exact day.
Chicago Half Marathon Pace Calculator & Race Plan
The Chicago Half is a flat out-and-back along Lake Shore Drive starting from Jackson Park near the Museum of Science and Industry. Only about 120 feet of total gain. The lakefront course is exposed to wind off Lake Michigan.
September in Chicago is usually good for running. Our model adjusts for the flat terrain and potential lakefront wind.
Chicago Half Marathon FAQ
When is the next Chicago Half Marathon?›
The next Chicago Half Marathon is on Sunday, September 27, 2026.
How long is the Chicago Half Marathon?›
The Chicago Half Marathon is 13.1 miles (21.097 km), the standard half marathon distance. It runs in Chicago, IL.
How much elevation gain does the Chicago Half Marathon have?›
The Chicago Half Marathon has about 297 ft (91 m) of climbing and 297 ft of descent, with a maximum grade of 10%.
Is the Chicago Half Marathon flat, downhill, or hilly?›
The Chicago Half Marathon starts and finishes at roughly the same elevation (net +0 m). With 297 ft of total climbing along the way, it's a fast, flat course.
How hard is the Chicago Half Marathon?›
Runner's Math scores the Chicago Half Marathon 34/100 (Moderate) — #10 of 16 half marathons in our library, ranked by modeled time cost. The profile costs about 0:20 versus a flat course for a runner at 4:00-marathon pace.
What's the weather usually like at the Chicago Half Marathon?›
Over the past 10 years on this date, median race-morning conditions were 65°F with a 53°F dew point and 12 mph wind. 6 of 10 years were warm enough to slow race pace.