A flat 5K through Grant Park and along the lakefront the morning before the marathon, ending at the marathon finish. October by the lake is usually cool, with wind the main variable.
Plan for about 52°F (11°C) at the 07:00 start, feeling like 47°F (8°C), with 79% humidity and 11 mph wind, warming to roughly 52°F (11°C) by the finish. It rained on 2 of the last 10 race days. Wear: Long Sleeve Tech Shirt, Capris or Light Tights, Running Shoes.
Feels like 47°F (8°C) at the start · finish 52°F (11°C) · rain 2 of 10 · start air from 35°F (2°C) to 68°F (20°C)
Conditions at the 07:00 start on the race's usual date each year (saturday before the Chicago Marathon). Years when the race was cancelled or moved still show that date's weather. Source: Open-Meteo ERA5 archive.
Bar: air temperature from start to finish · dot: feels-like effective temperature · ≫ windy (15+ mph) · rain · shaded: PR band 40–50°F
| Year | Start temp | Feels like | Finish | Humidity | Wind | Rain | Sky |
|---|---|---|---|---|---|---|---|
| 2025 | 58°F (14°C) | 56°F | 58°F | 79% | 5 mph | – | Clear |
| 2024 | 60°F (16°C) | 55°F | 60°F | 73% | 14 mph | 0.72 in | Clear |
| 2023 | 46°F (8°C) | 38°F | 46°F | 77% | 13 mph | – | Clear |
| 2022 | 39°F (4°C) | 32°F | 39°F | 87% | 8 mph | – | Mostly clear |
| 2021 | 64°F (18°C) | 66°F | 64°F | 90% | 6 mph | – | Drizzle |
| 2020 | 65°F (18°C) | 63°F | 65°F | 89% | 13 mph | – | Clear |
| 2019 | 38°F (3°C) | 27°F | 38°F | 62% | 14 mph | – | Clear |
| 2018 | 35°F (2°C) | 28°F | 35°F | 95% | 8 mph | – | Clear |
| 2017 | 68°F (20°C) | 64°F | 68°F | 80% | 19 mph | 0.26 in | Overcast |
| 2016 | 50°F (10°C) | 44°F | 50°F | 62% | 6 mph | – | Clear |
Coldest start: 35°F (2°C) in 2018. Warmest: 68°F (20°C) in 2017. Wettest: 0.72 in in 2024.
The time estimates apply published temperature–performance curves to this race's ten-year weather history. Performance peaks at an effective race temperature of roughly 40 to 50°F and degrades faster the warmer it gets and the slower you run (Ely et al., 2007; El Helou et al., 2012). Wind adds a cost that grows with the square of the wind speed (Pugh, 1971), split into head and tail components on point-to-point courses. Shorter races are penalised less. This is a model, not a prediction; your training and the course matter more.
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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 47°F (8°C)) with 79% humidity and 11 mph wind, warming to about 52°F (11°C) by the finish. It rained measurably on 2 of those 10 race days. The coldest start was 35°F (2°C) in 2018; the warmest was 68°F (20°C) in 2017.
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 Abbott Chicago 5K is usually held on saturday before the Chicago Marathon. The next expected date is Saturday, October 9, 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.
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