I imagine that you would need to disconnect the switch, it's likley to be shorting closed due to damp. I think the best and easiest way would be to look for a garage airline and blow around the switch area to move the water around, once you do that it'll probably spread it around thinly and dry it out, especially if it's 30deg ambient. You've not much to loose trying this first, before you start disassembling the switchgear.