A flat, fast loop through 29 neighborhoods from Grant Park. October by the lake has produced both record days and brutal heat.
By Brett Heimlich, part-time runner.
Plan for about 52°F (11°C) at the 07:00 start, feeling like 48°F (9°C), with 84% humidity and 9 mph wind, warming to roughly 59°F (15°C) by the finish. It rained on 1 of the last 10 race days. Wear: Long Sleeve Tech Shirt, Capris or Light Tights, Running Shoes.
52°F (11°C)
59°F (15°C)
1 of 10 years
39° to 69°F
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Conditions at the 07:00 start on the race's usual date each year (second Sunday of October). Years when the race was cancelled or moved still show that date's weather. Source: Open-Meteo ERA5 archive.
| Year | Start temp | Feels like | Finish | Humidity | Wind | Rain | Sky |
|---|---|---|---|---|---|---|---|
| 2025 | 51°F (11°C) | 49°F | 58°F | 90% | 5 mph | – | Clear |
| 2024 | 58°F (14°C) | 57°F | 60°F | 91% | 7 mph | – | Mostly clear |
| 2023 | 46°F (8°C) | 39°F | 51°F | 76% | 11 mph | – | Overcast |
| 2022 | 45°F (7°C) | 36°F | 58°F | 62% | 12 mph | – | Clear |
| 2021 | 69°F (21°C) | 67°F | 72°F | 83% | 17 mph | – | Overcast |
| 2020 | 58°F (14°C) | 56°F | 61°F | 90% | 9 mph | – | Drizzle |
| 2019 | 39°F (4°C) | 32°F | 48°F | 81% | 10 mph | – | Overcast |
| 2018 | 41°F (5°C) | 37°F | 52°F | 94% | 6 mph | 0.15 in | Clear |
| 2017 | 56°F (13°C) | 53°F | 68°F | 91% | 9 mph | – | Clear |
| 2016 | 54°F (12°C) | 51°F | 57°F | 81% | 6 mph | – | Clear |
Coldest start: 39°F (4°C) in 2019. Warmest: 69°F (21°C) in 2021. Wettest: 0.15 in in 2018.
Built from the 10-year average start conditions by the same engine as the live tool. Treat optional items as corral-only layers you can shed.
Long Sleeve Tech Shirt
Breathable moisture-wicking fabric
Capris or Light Tights
3/4 length for moderate warmth
Running Shoes
Your regular training shoes
✓ Worn by the author
Compression tight for 40 to 55°F, works under shorts
$78
✓ Worn by the author
Fast-drying micromesh tee for warm-weather miles
$75
Packable wind shell for cool morning miles
$115
✓ Worn by the author
Thin, ribbed quarter sock that keeps grit out
$36
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Over 2016 to 2025 the start averaged 52°F (11°C) (feels like 48°F (9°C)) with 84% humidity and 9 mph wind, warming to about 59°F (15°C) by the finish. It rained measurably on 1 of those 10 race days. The coldest start was 39°F (4°C) in 2019; the warmest was 69°F (21°C) in 2021.
For a typical 52°F (11°C) start: Long Sleeve Tech Shirt, Capris or Light Tights, Running Shoes. Dress for about 15°F warmer than the start temperature, since the race itself adds that much, and plan to shed anything you only need in the corral.
The Bank of America Chicago Marathon is usually held on second Sunday of October. The next expected date is Sunday, October 10, 2027. Confirm on the official site, since dates occasionally move.
The live forecast on this page comes from Open-Meteo and unlocks 16 days before the race. Forecasts inside 7 days are reliable for temperature within a few degrees; rain timing firms up in the last 2 to 3 days. Until then, the 10-year history above is the best planning guide.
Get a what-to-wear call for the live forecast at your exact location, free, no signup.
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