NOAA GFS (US National Oceanic and Atmospheric Administration) and DWD ICON (Deutscher Wetterdienst) are two of the models behind the forecast you see in almost every weather app. We grade both against the weather that actually happened, so this is a measured comparison rather than an opinion.
Short answer
The German model (ICON) scores higher in 1 of the 2 markets where we grade both. Both are graded against ERA5 reanalysis over a rolling 30-day window, scoring temperature, wind and rain. No model wins every day or every place, which is why we show them side by side.
Head to head, by market
CheckWeather Score — measured against recorded weather
Market
GFS
ICON
Winner
Australia300 cities
84±0.89°C temp · 88% rain
84±0.65°C temp · 84% rain
Tie
New Zealand237 cities
86±0.65°C temp · 89% rain
87±0.57°C temp · 88% rain
German
Scores blend temperature, wind and rain accuracy, each measured against ERA5 (the recorded weather) over a rolling 30-day window. Full method.
How they differ
same physics, different machines
American · GFS
The United States' flagship global model, fully open and updated four times a day. It powers a huge share of the free weather apps and tools on the internet.
Run by US National Oceanic and Atmospheric Administration Resolution ~13–25 km
German · ICON
Germany's national model, known for sharp handling of European and mid-latitude weather. Open data, and a favourite third option on power-user tools.
Run by Deutscher Wetterdienst Resolution ~13 km global / 2 km regional
Common questions
Is GFS more accurate than ICON?
In our own testing, German (ICON) comes out ahead across the 2 markets where both are graded. We measure each model's archived forecast against ERA5 reanalysis (the recorded weather) over a rolling 30-day window, scoring temperature, wind and rain. No model wins everywhere or every day, which is exactly why we show both side by side rather than picking one.
What is the difference between GFS and ICON?
NOAA GFS is run by US National Oceanic and Atmospheric Administration (United States) at roughly ~13–25 km resolution. DWD ICON is run by Deutscher Wetterdienst (Germany) at roughly ~13 km global / 2 km regional. They solve the same atmospheric physics with different code, different resolution and different data assimilation, which is why they disagree - and that disagreement is a useful signal about how certain the forecast really is.
Which should I trust for my forecast?
Neither on its own. When GFS and ICON agree, the forecast is reliable and you can plan on it. When they split, the day is genuinely uncertain and any single number is hiding that from you. That is why every city page on checkweather.io shows both models with a plain-English confidence score instead of one blended figure.