Both run a daily high-temperature market in 11 US cities. In 4 of them they settle on a different weather station, and in all 11 they read the station a different way.
138 of 329 city-days settled on different temperatures.
On those days the range Polymarket settled YES didn't hold the high Kalshi settled on: Polymarket came out warmer on 27 and cooler on 111.
| City | Kalshi settles on | Polymarket settles on | Last 30 days |
|---|---|---|---|
| Atlanta | Hartsfield-Jackson (KATL) | Hartsfield-Jackson International Airport (KATL) | 15 of 30 apart |
| Austin | Austin-Bergstrom (KAUS) | Austin-Bergstrom International Airport (KAUS) | 13 of 30 apart |
| Chicago | Midway (KMDW) | Chicago O'Hare Intl Airport (KORD)different station | 11 of 30 apart |
| Dallas | DFW Airport (KDFW) | Dallas Love Field (KDAL)different station | 9 of 30 apart |
| Denver | Denver International (KDEN) | Buckley Space Force Base (KBKF)different station | 12 of 30 apart |
| Houston | Hobby (KHOU) | William P. Hobby Airport (KHOU) | 9 of 30 apart |
| Los Angeles | LAX (KLAX) | Los Angeles International Airport (KLAX) | 15 of 29 apart |
| Miami | Miami International (KMIA) | Miami Intl Airport (KMIA) | 13 of 30 apart |
| New York City | Central Park (KNYC) | LaGuardia Airport (KLGA)different station | 21 of 30 apart |
| San Francisco | SFO (KSFO) | San Francisco International Airport (KSFO) | 13 of 30 apart |
| Seattle | Sea-Tac (KSEA) | Seattle-Tacoma International Airport (KSEA) | 7 of 30 apart |
"Apart": the range Polymarket settled YES didn't hold the high Kalshi settled on. Polymarket's winning range held the high Kalshi settled on for 191 of 329 days; it came out warmer on 27 and cooler on 111.
Even where the station is the same, the two markets count the high their own way.
| Rule | Kalshi | Polymarket |
|---|---|---|
| What counts as the high | The day's official high for the station, as The Weather Company publishes it for Kalshi (weather.com/kalshi) for events from Aug 14, 2026. It has matched the NWS climate report's official high on 1,587 of 1,588 settled days, and that high counts a peak between hourly reports. | The highest reading in the "Temp" column of NOAA's time-series page for the station, using its hourly data, in whole degrees. A peak between two readings isn't in that column, so it can come out lower than the official high. |
| The day | Midnight to midnight local standard time, so 1 AM to 1 AM while clocks are on daylight time. | Every time listed on that day on NOAA's page, which shows the station's local clock time. |
| The ranges | Two-degree brackets, with an open bracket at each end. Where the brackets start moves from day to day (61°–62° one day, 62°–63° another). | Two-degree ranges that start on an even number (62°–63°), with an open range at each end. |
| When it settles | After the final report for the day is out, usually the next morning. | Once the first reading of the next day is on NOAA's page, or by 11:59 PM Eastern the next day. If NOAA has no data by then, the Weather Underground daily observations table is used. |
Source: Polymarket's market rules (each daily event's description, read Thu, Oct 22); NOAA's station time series (LaGuardia shown); Kalshi contract terms; The Weather Company's Kalshi data
Polymarket runs a daily high in 39 more cities that Kalshi doesn't, most outside the US and in Celsius. The station each settles on:
| City | Station | Unit |
|---|---|---|
| Amsterdam | Amsterdam Airport Schiphol (EHAM) | °C |
| Ankara | Esenboğa Intl Airport (LTAC) | °C |
| Beijing | Beijing Capital International Airport (ZBAA) | °C |
| Buenos Aires | Minister Pistarini Intl Airport (SAEZ) | °C |
| Busan | Gimhae Intl Airport (RKPK) | °C |
| Cape Town | Cape Town International Airport (FACT) | °C |
| Chengdu | Chengdu Shuangliu International Airport (ZUUU) | °C |
| Chongqing | Chongqing Jiangbei International Airport (ZUCK) | °C |
| Guangzhou | Guangzhou Baiyun International Airport (ZGGG) | °C |
| Helsinki | Helsinki Vantaa Airport (EFHK) | °C |
| Hong Kong | Hong Kong Observatory | °C |
| Istanbul | Istanbul Airport | °C |
| Jeddah | King Abdulaziz International Airport (OEJN) | °C |
| Jinan | Jinan Yaoqiang International Airport | °C |
| Karachi | Jinnah International Airport (OPKC) | °C |
| Kuala Lumpur | Kuala Lumpur Intl Airport (WMKK) | °C |
| London | London City Airport (EGLC) | °C |
| Lucknow | Chaudhary Charan Singh Intl Airport (VILK) | °C |
| Madrid | Adolfo Suárez Madrid-Barajas Airport (LEMD) | °C |
| Manila | Ninoy Aquino International Airport (RPLL) | °C |
| Mexico City | Benito Juárez International Airport (MMMX) | °C |
| Milan | Malpensa Intl Airport (LIMC) | °C |
| Moscow | Vnukovo International Airport | °C |
| Munich | Munich Airport (EDDM) | °C |
| Panama City | Marcos A. Gelabert Intl Airport (MPMG) | °C |
| Paris | Paris-Le Bourget Airport (LFPB) | °C |
| Qingdao | Qingdao Jiaodong International Airport (ZSQD) | °C |
| Sao Paulo | Sao Paulo-Guarulhos International Airport (SBGR) | °C |
| Seoul (Incheon) | Incheon Intl Airport (RKSI) | °C |
| Shanghai | Shanghai Pudong International Airport (ZSPD) | °C |
| Shenzhen | Shenzhen Bao'an International Airport (ZGSZ) | °C |
| Singapore | Singapore Changi Airport (WSSS) | °C |
| Tel Aviv | Ben Gurion International Airport | °C |
| Tokyo | Tokyo Haneda Airport (RJTT) | °C |
| Toronto | Toronto Pearson Intl Airport (CYYZ) | °C |
| Warsaw | Warsaw Chopin Airport (EPWA) | °C |
| Wellington | Wellington Intl Airport (NZWN) | °C |
| Wuhan | Wuhan Tianhe International Airport (ZHHH) | °C |
| Zhengzhou | Zhengzhou Xinzheng International Airport | °C |
From Polymarket's market rules, read Thu, Oct 22.
Today in New York City, live · How Kalshi's markets settle
Almanac shows information and tools. It never says what to buy or sell and never places an order.