Need help for creating a rule for automatic ventilation

[rossko57]

@mpuff

Weather_Snow_Volume_today is a unit of measurement

Yes, you will need to take that into account in your rule.
Try this

[SOLVED] Comparaison with OpenWeatherMap temperature

Your Item has UoM, Units of Measurement. So it’s effectively 15 °C not just 15, and comparing with just 12 is apples-and-oranges. This is one of the clumsier parts of UoM. You can either extract just-the-number or compare with a temperature. if( (localHourlyForecast12Temperature.state as QuantityType<Number>).intValue <= 12 ) if( localHourlyForecast12Temperature.state <= 12 | "°C" )