For instance this was accuracy result for Prague in data collected over 6 weeks in forecasts where sources provided different forecast (how many out of 6 correct): AerisWeather 5.5, Foreca 4, MET Norway 4, AccuWeather 2, Dark Sky 1.5, WeatherBit 1.5, Open Weather 1, World Weather Online 1
And I still keep collecting these data and it's not changing.