US · America/Chicago
Kalshi, IBKR and Polymarket US settle Chicago temperature on KMDW
KMDW is Midway International, Chicago. Kalshi and IBKR ForecastEx and Polymarket US settle temperature contracts here. Below: the resolution source each venue names, when the station reports, and how long a reading takes to reach the public feed.
Kalshi and IBKR ForecastEx and Polymarket US use KMDW (Midway International). Polymarket settles the same city on KORD (O'Hare International) instead. The two sites can report different temperatures at the same moment and land in different contract buckets on the same day, so a reading from one tells you nothing definitive about the other.
How it settles
| Venue | Resolution source | Unit | Bucket | Contracts |
|---|---|---|---|---|
| Kalshi | NWS Climatological Report (CLI), relayed by The Weather Company Source code CLIMDW. The daily climatological report is compiled from the full one-minute record, so it can print a high that the hourly reports never showed. Its day runs in local standard time all year. | Fahrenheit | 2°F Range contract | high · lowKXHIGHCHI, KXLOWTCHI |
| IBKR ForecastEx Also sold through Robinhood: same ticker, same settlement. | Weather Underground daily history table for this station Source code KMDW. That table carries hourly METARs and SPECIs only, over the local clock day, and prints whole degrees rounded. | Fahrenheit | 1°F ladder Exceeds X, one rung per degree | high · lowUHMDW, ULMDW |
| Polymarket US | NWS Climatological Report (CLI) for this station Source code CLIMDW. The daily climatological report is compiled from the full one-minute record, so it can print a high that the hourly reports never showed. Its day runs in local standard time all year. | Fahrenheit | 2°F Range contract | hightemp-mdwhigh |
Reporting and delay
Questions
Which weather station settles Chicago temperature contracts?
Kalshi, IBKR ForecastEx and Polymarket US settle Chicago on KMDW, Midway International. Polymarket settles the same city on KORD, O'Hare International, which is a different site.
What is the resolution source for Kalshi Chicago temperature?
Kalshi names NWS Climatological Report (CLI), relayed by The Weather Company. Contracts settle in Fahrenheit, on 2-degree buckets. The daily climatological report is compiled from the full one-minute record, so it can print a high that the hourly reports never showed. Its day runs in local standard time all year.
What is the resolution source for IBKR ForecastEx Chicago temperature?
IBKR ForecastEx names Weather Underground daily history table for this station. Contracts settle in Fahrenheit, as a ladder of contracts one degree apart that pay when the day's reading passes the strike. That table carries hourly METARs and SPECIs only, over the local clock day, and prints whole degrees rounded. Robinhood resells this same contract, at the same ticker and settlement.
What is the resolution source for Polymarket US Chicago temperature?
Polymarket US names NWS Climatological Report (CLI) for this station. Contracts settle in Fahrenheit, on 2-degree buckets. The daily climatological report is compiled from the full one-minute record, so it can print a high that the hourly reports never showed. Its day runs in local standard time all year.
When does KMDW report?
:53 past each hour, UTC — 1 regular report per hour.
How long does a KMDW observation take to become public?
Measured over 26 hours on 2026-09-17, the median delay from the observation time in the report to its arrival on the public NOAA feed was 3 min 32 s, with a 90th percentile of 3 min 38 s across 29 reports. This moves with upstream conditions and is not a service level.
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