Windsplit · race guide · Chicago, USA
Bank of America Chicago Marathon starts Sunday 11 October 2026 at 07:30 local time from Grant Park. Below: the live forecast for race day, which parts of the course take the wind, the elevation profile and how to turn it into a pacing plan.
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Flat loop through 29 neighbourhoods with start and finish in Grant Park. Long straight north–south stretches make the wind direction decisive.
Numbers are km markers. North is up.
69 m up, 68 m down, 177–184 m above sea level. 10 m between grid lines.
Computed from the direction the course runs in each kilometre. A kilometre counts as headwind when the wind comes from within 60° of straight ahead, and as tailwind when it comes from within 60° of straight behind. Find the forecast wind direction and read your row.
| Wind from | Headwind km | Tailwind km | Headwind share |
|---|---|---|---|
| N (north) | 1, 5–12, 39–42 | 3, 14–22, 28, 30–31, 33, 35, 37 | 31 % |
| NE (north-east) | 1, 5–9, 11, 26–27, 32, 34, 39–42 | 3, 15, 17, 19–25, 29–30, 37 | 36 % |
| E (east) | 26–27, 32, 34, 36 | 2, 23–25, 29 | 12 % |
| SE (south-east) | 3, 14–20, 26–28, 31–32, 34–37 | 1, 5–12, 23–24, 39–41 | 40 % |
| S (south) | 3, 14–22, 28, 30–31, 33, 35, 37 | 1, 5–12, 39–42 | 38 % |
| SW (south-west) | 3, 15, 17, 19–25, 29–30, 37 | 1, 5–9, 11, 26–27, 32, 34, 39–42 | 31 % |
| W (west) | 2, 23–25, 29 | 26–27, 32, 34, 36 | 12 % |
| NW (north-west) | 1, 5–12, 23–24, 39–41 | 3, 14–20, 26–28, 31–32, 34–37 | 33 % |
69 m of climbing and 68 m of descent over 42.195 km, between 177 and 184 m above sea level. Flat loop through 29 neighbourhoods with start and finish in Grant Park. Long straight north–south stretches make the wind direction decisive.
It depends on the wind direction on the day. With a wind from the south-east, the course has a headwind on km 3, 14–20, 26–28, 31–32, 34–37 (40 % of the distance) and a tailwind on km 1, 5–12, 23–24, 39–41. The table on this page lists all eight directions; the race plan uses the actual forecast hour by hour.
Windsplit shows a forecast from 16 days out, but wind forecasts usually converge in the last three days. Check the evening before and again on race morning: the tool refreshes every 30 minutes, and the confidence line shows whether the models agree.
Yes. Replay reads the activity from Strava or a GPX/FIT file, fetches the weather that was recorded along the route, and shows the wind, hill and heat cost per kilometre, plus an adjusted pace in still air. If you planned the race in Windsplit on the same device, it compares the prediction with the result.