During winters, when you exhale on the glass of your mirror, what happens. If you try to do this in summer why doesn’t this happen?

For precipitation to occur, the conditions should be humid and the moisture content in the air must be high.

In winters, the air that we exhale, is hotter than the air that is present surrounding the window glass. Hence, when the hot air from our mouth touches the cool surface of the window glass, it precipitates to form water droplets.

In summers, the air that we exhale, is cooler than the air that is present surrounding the window glass. Hence, when the cool air from the mouth touched the hot surface of the window, no precipitation occurs and no water droplets are formed.

Precipitation usually occurs only when hot air touches cooler surfaces.