openpatchlab/polymarket-weather-trading-bot

WeatherBet is a TypeScript bot that automatically trades weather-related prediction markets on Polymarket, a decentralized platform where people bet on real-world event outcomes. Specifically, it targets markets asking questions like "Will Chicago's temperature peak at 46-47 degrees Fahrenheit on this date?", and tries to find cases where the crowd's pricing is wrong relative to what actual weather forecasts say. The bot pulls temperature data from three sources: ECMWF (a European global weather model), HRRR and GFS (high-resolution US models updated hourly), and METAR observations from airport weather stations. The airport station data matters because Polymarket resolves these markets against official airport METAR readings, not general city-center estimates. The bot maps each city to its correct airport station (for example, New York City resolves to LaGuardia, not JFK). When a market's crowd-implied probability diverges enough from what the weather models say, the bot calculates an expected value, the average profit per dollar bet, and if that value is positive and large enough, it places a trade sized using the Kelly Criterion (a formula that bets proportionally to your edge to grow a bankroll optimally without blowing up). It also applies stop-loss rules, filters out illiquid markets, and tracks its own forecast accuracy city by city to self-calibrate over time. Paper trading (simulated with no real money) is the default, live trading requires a Polygon wallet private key. Requires Node.js 20.10 or newer.