Kalshi's Chicago market settles on the daily high at Midway (KMDW), not O'Hare, as the climate report CLIMDW and The Weather Company publish it. Series KXHIGHCHI, listed since Aug 19, 2021.
Updated Oct 30, 5:21 AM CDT: newest final official high is for Thu, Oct 29.
Chicago Midway International Airport
Not O'Hare.
1:00 AM Oct 31 to 1:00 AM Nov 1 CDT
Midnight to midnight CST, local standard time: 1:00 AM to 1:00 AM on Chicago's clock while daylight saving is on.
Today's six brackets, in whole degrees
Since Aug 14, 2026, 4 of 77 days (5%) settled on a tail bracket: 3 below the bottom bracket and 1 above the top one. In the last 30 days: 2 of 30.
| Day | Settled on | Winning bracket | Time of high (LST) | Settled at |
|---|---|---|---|---|
| Thu, Oct 29 | 69° | 68° to 69° | 3:17 PM | Oct 30, 7:08 AM CDT |
| Wed, Oct 28 | 76° | 76° to 77° | 3:29 PM | Oct 29, 7:08 AM CDT |
| Tue, Oct 27 | 69° | 68° to 69° | 5:37 PM | Oct 28, 7:08 AM CDT |
| Mon, Oct 26 | 64° | 64° to 65° | 11:35 AM | Oct 27, 7:08 AM CDT |
| Sun, Oct 25 | 74° | 74° to 75° | 2:17 PM | Oct 26, 7:08 AM CDT |
| Sat, Oct 24 | 70° | 70° to 71° | 2:30 PM | Oct 25, 7:08 AM CDT |
| Fri, Oct 23 | 71° | 71° to 72° | 2:41 PM | Oct 24, 7:08 AM CDT |
| Thu, Oct 22 | 72° | 72° to 73° | 2:41 PM | Oct 23, 7:08 AM CDT |
| Wed, Oct 21 | 71° | 70° to 71° | 3:11 PM | Oct 22, 7:08 AM CDT |
| Tue, Oct 20 | 69° | 69° to 70° | 1:41 PM | Oct 21, 7:08 AM CDT |
| Mon, Oct 19 | 68° | 67° to 68° | 3:14 PM | Oct 20, 7:09 AM CDT |
| Sun, Oct 18 | 64° | 63° to 64° | 4:01 PM | Oct 19, 7:13 AM CDT |
| Sat, Oct 17 | 56° | 55° to 56° | 3:48 PM | Oct 18, 7:08 AM CDT |
| Fri, Oct 16 | 58° | 59° or belowbottom tail | 2:50 PM | Oct 17, 7:08 AM CDT |
| Thu, Oct 15 | 66° | 65° to 66° | 9:17 PM | Oct 16, 7:08 AM CDT |
| Wed, Oct 14 | 67° | 67° to 68° | 2:33 AM | Oct 15, 7:08 AM CDT |
| Tue, Oct 13 | 79° | 81° or belowbottom tail | 2:39 PM | Oct 14, 7:08 AM CDT |
| Mon, Oct 12 | 88° | 88° to 89° | 3:44 PM | Oct 13, 7:08 AM CDT |
| Sun, Oct 11 | 78° | 77° to 78° | 3:56 PM | Oct 12, 7:08 AM CDT |
| Sat, Oct 10 | 81° | 81° to 82° | 2:25 PM | Oct 11, 7:08 AM CDT |
| Fri, Oct 9 | 74° | 73° to 74° | 2:45 PM | Oct 10, 7:08 AM CDT |
| Thu, Oct 8 | 73° | 72° to 73° | 3:06 PM | Oct 9, 7:08 AM CDT |
| Wed, Oct 7 | 79° | 78° to 79° | 3:28 PM | Oct 8, 7:08 AM CDT |
| Tue, Oct 6 | 74° | 74° to 75° | 3:38 PM | Oct 7, 7:09 AM CDT |
| Mon, Oct 5 | 68° | 68° to 69° | 11:48 AM | Oct 6, 7:09 AM CDT |
| Sun, Oct 4 | 74° | 74° to 75° | 2:09 PM | Oct 5, 7:09 AM CDT |
| Sat, Oct 3 | 70° | 70° to 71° | 3:50 PM | Oct 4, 7:09 AM CDT |
| Fri, Oct 2 | 65° | 65° to 66° | 2:18 PM | Oct 3, 7:09 AM CDT |
| Thu, Oct 1 | 72° | 71° to 72° | 11:41 AM | Oct 2, 7:09 AM CDT |
| Wed, Sep 30 | 70° | 69° to 70° | 1:15 AM | Oct 1, 7:09 AM CDT |
Source: Each market's result, settlement value and time: Kalshi's public market data; Time of the high: NWS climate reports for KMDW, via IEM
Over 365 days (Oct 30, 2025 to Oct 29, 2026), the median time of the official high was 3:09 PM local standard time, and half the highs came between 1:27 PM and 4:26 PM. Over the last 60 days the median was 2:54 PM.
Midway's high came before 1 AM standard time (1 to 2 AM daylight time) on 17 of 365 days (5%): the climate day's warmest minutes were its first.
KMDW report times, standard time.
Source: NWS climate reports for KMDW, via IEM; IEM table of NWS climate reports
Kalshi's Chicago market settles on Midway (KMDW) and nothing else. O'Hare International Airport (KORD) publishes its own climate report, with its own daily high, which doesn't count.
O'Hare International Airport (KORD) against Midway, 27 km apart
Over 365 days (Oct 21, 2025 to Oct 20, 2026), the two official highs were the same whole degree on 134 of 365 days (37%). O'Hare was warmer on 82 and cooler on 149, −0.3°F on average, and 2°F or more apart (a bracket's width) on 70.
Widest gaps: Apr 22, 2026, KORD 73° and KMDW 68°; Mar 6, 2026, KORD 66° and KMDW 74°.
Source: NWS climate reports for KORD (CLIORD), via IEM; NWS climate reports for KMDW, via IEM
Polymarket's Chicago market settles on Chicago O'Hare Intl Airport (KORD), not Midway (KMDW): the highest of its hourly readings in whole °F, over the local calendar day, in 2°F ranges. The two exchanges can settle the same day differently.
Kalshi vs Polymarket in Chicago: the stations and the last 30 days side by side
On 182 days from May 1, 2026 to Oct 29, 2026, the NWS's afternoon preliminary report (usually "as of 4 PM" local time) had the same high as the final report on 156 of 182 days (86%). The final report came in higher on 26 and never lower.
25 of those 26 higher finals put the high after the 4 PM cutoff.
Source: Every NWS climate report issued for KMDW (CLIMDW), via IEM's text archive
The normal high for Oct 31 is 56°F and the record high is 84°F. The normal falls to 43°F by Nov 30.
365 final highs at KMDW, Oct 30, 2025 to Oct 29, 2026, against the normal and record each report printed.
Source: NWS climate reports for KMDW, via IEM; NOAA NCEI U.S. Climate Normals
Climate-report stations near Midway, and how their official highs ran against it. None settles the Chicago market.
Straight-line distances from KMDW; snapshot Oct 21, 2026.
Source: IEM's list of NWS climate-report sites; aviationweather.gov station information
Chicago Midway International Airport (KMDW), the station named by the climate-report code CLIMDW in the market's rules. Not O'Hare.
Midnight to midnight CST, local standard time. During daylight saving that is 1:00 AM Oct 31 to 1:00 AM Nov 1 CDT.
Trading closes at 1:00 AM CDT after the day ends. Over the last 77 settled days the result posted a median of 6.2 hours after close.
59° or below, 60° to 61°, 62° to 63°, 64° to 65°, 66° to 67°, 68° or above, compared with Midway's published whole-degree high. The two tails are strict.
On 4 of 77 settled days from Aug 14, 2026 to Oct 29, 2026 (5%): 3 on the bottom tail and 1 on the top tail.
Over 365 days to Oct 29, 2026, the median time of the official high at KMDW was 3:09 PM local standard time. On 17 of those days it came before 1 AM standard time.
From May 1, 2026 to Oct 29, 2026, the afternoon preliminary report's high matched the final report's on 156 of 182 days. The final was higher on 26 and lower on 0.
No. Only Midway (KMDW) does. Over 365 days to Oct 20, 2026, KORD's official high was the same whole degree as KMDW's on 134 days and 2°F or more apart on 70.
The rules every city shares · Reading CLIMDW · The Aug 14, 2026 change
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