Wait for rain.

Here it is how it looks: http://steamcommunity.com/sharedfiles/filedetails/?id=229318122

I've also encountered a rain at abandoned ship during a glitch in a room without exits. There was also raining there but I was as well getting wet there (all of my outfit items got terribly wet). Haven't tried to get wet inside the building, the rain just stopped. Will try to give more details about getting wet inside and if there are only some buildings with "no roof" or it just rains in every building.