Should you open the windows or not?
If you are trying to control the humidity level of your home, it is useful to know the water moisture content of the outside air. The weather is usually displayed in such a way that it’s difficult to know what the actual humidity of the outside air is relative to the humidity inside.The temperature is likely not the same inside and out. As humidity is affected by temperature, the humidity of the outside air at the outside temperature is not the humidity when it has changed temperature to match the inside.
This simple humidity calculator will all of this for you, just enter the outside temperature and humidity, then the inside temperature that the air will be cooled/heated to, and the resulting humidity will be calculated.