# Weather for prediction-market agents (Kalshi & Polymarket temperature markets)

Station-exact temperature data for agents trading Kalshi daily high/low markets and Polymarket "highest/lowest temperature in <city>" markets.
70 settlement stations: 24 Kalshi (NWS CLI climate locations) and 53 Polymarket cities. Free list: GET https://weather-x402.linholiday.workers.dev/stations

Paid endpoints (x402 v2, scheme "exact", USDC on eip155:8453, payTo 0xA94AaF06ad79baD31E0DF25187d376780a8836c6):
  GET https://weather-x402.linholiday.workers.dev/forecast?station=KNYC&date=YYYY-MM-DD   0.02 USDC  high/low forecast on the settlement day window: NWS gridpoint + MET Norway, consensus + spread (F and C)
  GET https://weather-x402.linholiday.workers.dev/observed?station=KLGA                   0.01 USDC  max/min observed so far today (METAR/SPECI + 6/24h groups), Kalshi LST climate day and Polymarket local day
  GET https://weather-x402.linholiday.workers.dev/settlement?station=KMDW&date=YYYY-MM-DD 0.01 USDC  official NWS CLI high/low (Kalshi settlement: first non-preliminary report) + Polymarket-style value from hourly readings
  GET https://weather-x402.linholiday.workers.dev/market-station?q=KXHIGHNY-26OCT21-B88.5 0.01 USDC  ticker / Polymarket slug / city -> settlement station, CLI code, day window, units, strike range, station traps
Requests without payment get the 402 challenge. Invalid input returns HTTP 400 and upstream outages return 502; in both cases the payment is NOT settled, so you are never charged for an error.

Free previews (fixed inputs): /preview/forecast, /preview/observed, /preview/settlement, /preview/market-station

Settlement rules (researched 2026-10-21; the market's own rules always win):
- Kalshi: Daily high/low settle on the first non-preliminary NWS Daily Climate Report (CLI) for the named climate location (e.g. CLINYC = Central Park), whole degrees F. The climate day is midnight to midnight local STANDARD time (during DST that is 1:00 AM to 1:00 AM local clock time). Source: Kalshi market rules / help.kalshi.com.
- Polymarket: Highest/lowest reading in the 'Temp' column of NOAA's weather.gov/wrh/timeseries page for the named station for the local calendar day (US markets use hourly data, F; others C). Weather Underground is a fallback only if NOAA data is unavailable. Source: Polymarket market rules.
- Station traps: NYC Kalshi=KNYC Central Park vs Polymarket=KLGA LaGuardia; Chicago KMDW vs KORD; Dallas KDFW vs KDAL; Denver KDEN vs KBKF.

Data sources and licenses:
- US National Weather Service (api.weather.gov) gridpoint forecast: US public domain (NWS disclaimer: weather.gov/disclaimer) (https://api.weather.gov)
- NWS Daily Climate Report (CLI) via api.weather.gov/products: US public domain (https://api.weather.gov/products/types/CLI)
- NOAA/NWS Aviation Weather Center METAR data API (aviationweather.gov): US public domain; non-US METARs are WMO-exchanged observations redistributed by NOAA (https://aviationweather.gov/data/api/)
- MET Norway Locationforecast 2.0 (api.met.no): CC BY 4.0, data from The Norwegian Meteorological Institute (MET Norway); values aggregated (daily max/min) by this service (https://api.met.no/doc/License)
Contains data from MET Norway under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/); values are aggregated to daily max/min. NWS data is public domain; this service is not affiliated with or endorsed by NOAA/NWS, MET Norway, Kalshi or Polymarket.
Not financial advice. Forecasts are uncertain; observed values are unofficial until the official report.
Contact: lin.chang2007@mailfence.com