ECMWF IFS (European Centre for Medium-Range Weather Forecasts) and ECCC GEM (Environment and Climate Change Canada) 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 European model (ECMWF) scores higher in 1 of the 1 market 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
ECMWF
GEM
Winner
Canada300 cities
87±0.8°C temp · 90% rain
75±1.61°C temp · 82% rain
European
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
European · ECMWF
Widely regarded as the world's most accurate global model. Run by a 35-nation European agency, its high-resolution forecast is the benchmark others are measured against.
Run by European Centre for Medium-Range Weather Forecasts Resolution ~25 km (open 0.25° release)
Env. Canada · GEM
Canada's national model, built for a country of extreme cold snaps and fast-moving systems. Published as open data by Environment Canada.
Run by Environment and Climate Change Canada Resolution ~15 km global
Common questions
Is ECMWF more accurate than GEM?
In our own testing, European (ECMWF) comes out ahead across the 1 market 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 ECMWF and GEM?
ECMWF IFS is run by European Centre for Medium-Range Weather Forecasts (EU (Reading, UK)) at roughly ~25 km (open 0.25° release) resolution. ECCC GEM is run by Environment and Climate Change Canada (Canada) at roughly ~15 km global. 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 ECMWF and GEM 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.