Very common. There are several threads here on this very issue. Step 1 is to yank the big round "rubber caps" off the back of the headlights, there are two on each side. Let the light dry out over a few days time.
There was a "vent kit" available at one time, I am not sure those are still available. Anyway, yank all four vent caps off for now.

Others with more energy than I have tonight will chime in.