The exact hours that count toward a city's daily high on Kalshi (local standard time) and Polymarket (the local calendar day), with Kalshi's open, close and results.
Polymarket: New York City's day for Saturday, October 31, 2026 at KLGA runs
Sat, Oct 31, 12:00 AM EDT to Sun, Nov 1, 12:00 AM EDT
Midnight to midnight on the clock, daylight saving included. That's an hour off Kalshi's day below: a reading at 12:30 AM counts toward this day on Polymarket and toward the day before on Kalshi.
Kalshi: New York City's high for Saturday, October 31, 2026 is taken from
Sat, Oct 31, 1:00 AM EDT to Sun, Nov 1, 1:00 AM EDT
Daylight saving is on, so the day runs 1 AM to 1 AM on the clock: a reading at 12:30 AM still counts toward the day before.
The NWS's final climate report for the day comes out between 12:30 and 5:00 AM local time; The Weather Company's settlement page shows the day as "no report" until after the day ends. In UTC: 2026-10-31 05:00 to 2026-11-01 05:00.
The day is the NWS climate day: midnight to midnight local standard time. It doesn't move for daylight saving, so in summer it runs 1 AM to 1 AM on the clock, and a reading at 12:30 AM counts toward the day before. Phoenix keeps standard time all year.
Since the Aug 14, 2026 events, trading closes when the day ends, at midnight standard time, in every city. Each market opens at 10:00 AM Eastern the day before. Across 1,800 settled city-days, half the results posted within 6.2 hours of the close and nine in ten within 7.2 hours.
Polymarket's temperature markets count the local calendar day instead: midnight to midnight on the clock, daylight saving included, in its US and world cities alike. In summer the two exchanges' days are an hour apart.
Source: NWS Chicago: weather observations FAQ (the climate day); NWS Instruction 10-1004 (when the final report is issued); Open, close and settlement times: Kalshi's public market data; Kalshi contract terms
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