Why does my ceiling only get wet in the winter?

This home owner has an interesting problem. She does not seem to have a roof leak, but in the winter a water stain appears on the ceiling in a second floor room of her 2-storey house. Do you have any ideas why this is happening? The stain always dries up on the summer.

Why does my ceiling only get wet in the winter? first appeared on www.roofer911.com