condensation behind gpx screens

Was wondering if anybody else has had this problem now that the cold weather is here.
I was thinking of wrapping the control box with a towel when not using,to see what happens.  

This Happened to me the other week when detecting for the whole four hours.
It was a fine mist behind the front screen a did not go away.
I could just make out the settings on the screen  

Mine fogged up Saturday (first time)day was like a sleety fog.only 10 from home so I packed up.bugger me if the Chinese Rolex didn't fog up as well.

All cleared up now.
Just remembered on my first detecting outing it was a crap day ,a bit of rain, so I placed a plastic bag over control box and white patch marks began to appear behind the screen so put detector back in car and patches disappeared as quickly they came.