Which forecast is right?
The big weather models, scored against what weather balloons really measured near the ground.
Latest comparisons
How it works
Groundcheck collects readings from weather balloons (radiosondes). For every balloon, the reading closest to the ground gives the real temperature and humidity at a known place and hour.
For that place and hour, the page asks Open-Meteo's archive of past model runs what each model had predicted: the newest forecast, the one made 1 day earlier, and the one made 2 days earlier. The difference between the forecast and the balloon's measurement is the model's mistake.
What the numbers mean. "Average mistake" is the mean size of the error. "Too warm / cool" is the average direction of the error: a model that is +1.5° is usually too warm. "Within 1°" is the share of forecasts that missed by one degree or less.
Limits. Balloons are launched in certain places at certain times, so this says how models do near balloon launch sites, mostly in Europe. A model's grid point is not at the balloon's height, so forecasts are corrected by 0.65° per 100 m of difference. Weather apps (Apple, Google and others) are not included: they have no public archive to check against. Updated daily.