Getting a little water in the oil from the cowl vent is sure better than the alternate. I had an engine with a crack in the cylinder wall that developed what I called chocolate pudding. That required a replacement engine. You should be able to deal with it by draining the milkshake out and doing a couple short duration oil changes. Be sure to get the engine nice and warm a few times to help evaporate the water.
Oh, and don't stand out in the rain with your mouth open so to speak.
