The GPS signals will not be affected by clouds, rain, fog,snow, etc., because of the combination of their passing through water vapor, and the signal wavelength meaning they "pass through" rain etc.

For example: GPS smart bombs. Planes taxi using GPS in heavy fog, etc.

Now, on the other hand, water will block/attenuate GPS signals. Dry you antenna off if it is wet or damp from fog,rain etc. This will help a lot fellers and fellerettes. MOAO