General primers on how these prediction markets work are available in the IBKR prediction markets FAQ and the ForecastEx FAQ.
A market in which each contract pays one dollar if a stated weather outcome occurs and nothing if it does not, so the contract's price is the market's probability of that outcome. ForecastEx lists these on daily high and low temperatures at individual weather stations, on Atlantic named storm and hurricane counts, and on major hurricane landfall by location, among many others.
See the accuracy page, the day-by-day scorecard, and the working paper Improvement of Daily Temperature Forecasts from a Prediction Market (Brown, 2026, EarthArXiv preprint).
ForecastEx does not publish a single forecast temperature. It lists a ladder of contracts at different strikes, and each price is the ForecastEx probability that the day's extreme passes that strike. Comparing ForecastEx with the other systems therefore requires converting that ladder into a central estimate. The 50 percent level is the ForecastEx implied median, so where two adjacent listed strikes bracket that crossing, the central value is interpolated between them. Where the ladder does not bracket 50 percent, because every listed strike sits far in or far out of the money, no central value is recorded and ForecastEx is left unscored rather than extrapolated beyond the quoted ladder. That reflects how the strikes happened to be listed rather than anything about forecast quality, so it should count neither for nor against ForecastEx. On the accuracy page and in the working paper the ladder is first made to fall as the strike rises, the crossing is then rounded up to a whole degree for highs and down for lows to match whole-degree settlement, and a crossing that would have to be read across two or more unpriced strikes is left undefined.
Every forecast cycle is archived as published, because no public endpoint returns an earlier forecast. Each tool on the city chart and the panels under it is drawn from its own rows: the NWS hourly forecast, the Blend of Models’ hourly bulletin carried on by its 3-hourly one, GFS MOS’s 3-hourly rows, LAMP’s hourly rows, and the HRRR, NOAA’s 3 km model run every hour, read at the grid point nearest each station. Each tool’s newest run is drawn solid in the tool’s color, and the runs it superseded are dotted in the same color. “As issued” means the source’s last run issued before local midnight at the station. The high and low beside the chart are the highest and lowest row of that run inside the day, so they hold still while the day’s observations come in; on the day-ahead view they follow the newest runs until midnight. Each level line spans exactly the hours its rows cover. Day boundaries are the station’s local calendar day through its IANA time zone. The map shading is an inverse-distance interpolation of the listed stations’ NWS forecasts and is labeled derived; it is not an NWS product. Nothing here is an official National Weather Service product, and nothing implies endorsement by or affiliation with NOAA or the NWS.
All four commonly referenced forecast systems rely on physical numerical weather prediction models that solve the equations of the atmosphere forward in time. ECMWF (the European model) and GFS (the American model) are shown here in their raw form. Raw physical models are flexible and can handle weather situations they have never seen (they are not explicitly trained on historical data but rather adhere to the laws of physics), but forecasts apply to a relatively large discrete grid box that contains the weather station rather than the single point where the station sits, causing them to carry systemic biases relative to the stations.
The Aviation Forecast is a model output statistics system. It compares historical forecasts from physical models with what actually occurred and uses the errors to statistically correct systemic biases at the level of individual weather stations. The tradeoff is that a statistical fit is anchored in past situations and bends less readily to a genuinely unusual one. The National Weather Service's National Digital Forecast Database is undergirded by the National Blend of Models but layers on human forecasters' judgment, which is more flexible in dynamic weather situations but introduces subjective judgment.
Every forecast system this site compares, with what it is and a link to its documentation, is listed at the foot of the accuracy page, along with every other data source behind these pages.
Prediction market basics
Temperature markets and energy
Hurricane and climate contracts
Climate contracts