Race-day weather · Wyndo for runners
Chicago Half Marathon weather
September 27, 2026 · Chicago, IL · scheduled start 7:00 AM (America/Chicago). What the start usually feels like, year by year — and a live start-time read once the race is inside the 7-day forecast window.
Countdown
30 days to race day
The live race-day forecast unlocks 24 days from now, when September 27, 2026 enters the 7-day forecast window — a start-time read for the scheduled 7:00 AM start. Until then, live hourly data is not available; the history below shows what race morning usually looks like.
Typical start temp
63°F
median of 3 years
A warm year
65°F
75th percentile start temp
Rain at the start
0%
0 of 3 measured years
Race-morning weather history
Late-September Chicago lakefront: mild-to-warm (~55-72°F), lake humidity, occasional early-fall heat — typical-climate characterization, UNVERIFIED; ERA5 supplies actuals. 2020 CANCELLED (COVID). No other cancelled/virtual years found (search not exhaustive). Wyndo tracks what past editions of the race actually served up at the start hour — temperature, dew point, wind, and rain, and reads the live forecast for the start once race week arrives.
Median start temp
63°F
p75 (a warm year): 65°F
Median dew point
60°F
at the start hour
Rain at the start
0%
0 of 3 measured years
Warmest start
65°F
in 2024
Scroll sideways to see all columns.
| Year | Start temp | Dew point | Wind | Precip (start hr) | Day's high |
|---|---|---|---|---|---|
| 2025 | 63°F | 62°F | 5 mph | dry | 76°F |
| 2024 | 65°F | 60°F | 9 mph | dry | 71°F |
| 2023 | 58°F | 53°F | 6 mph | dry | 77°F |
Each row is the weather at a real past edition's date and this race's current start hour (ERA5 reanalysis at the start line).
Your heat-adjusted goal for the half marathon
The same cited model as the full calculator, pointed at this race: the median start-hour conditions this calendar slot has served up — climatology, not a forecast.
Your race-day brief
Skip the taper-week refresh spiral. Email briefs for the Chicago Half Marathon: a start-hour outlook when race day enters the 7-day forecast window, updates only when it changes meaningfully, and a final look the day before.
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Race facts
- Start line
- E. Hayes Drive in Historic Jackson Park (site of the 1893 World's Columbian Exposition, near the Museum of Science and Industry); out-and-back up the lakefront. Coordinate is a Nominatim geocode of E. Hayes Dr — approximate.
- Scheduled start
- 7:00 AM (America/Chicago) — Half 7:00 AM, Para-athlete half start 6:57 AM, 5K 7:45 AM. Source: chicagohalfmarathon.com/half-marathon (2026) [V].
- Field size
- fieldSize is 2023 half-marathon finishers (7,253, Webscorer) [V]. The scout's "~15-18k" was NOT carried — that figure conflates distances/registrants: FOX32 reported ~10,000 total participants across half+5K in 2024, and half-only finishers run ~7-7.5k. Recent editions (2024/2025) sold out at similar scale; historic high was 13,537 half finishers in 2009. OPEN QUESTION: a current half-only finisher count (2024/2025) if a cleaner source surfaces.
- Registration
- open (Special Events Management / RunSignup; recent editions sold out)
Wyndo is not affiliated with or endorsed by the Chicago Half Marathon (officially the "Life Time Chicago Half Marathon") or its organizers. Race names are used descriptively to identify the event; schedules and start times belong to the race — always confirm details on the official site. Weather guidance here is informational, never medical advice, and event alert flags on race day belong to the race's own medical team.