Yeah I read your post which made me worry cause originally I thought it was just the rain etc and didnt think it could be anything else lol well... i havent seen any signs of steam today! Yesterday morning my car was iced up and i noticed it when I got to work so like you say the cold and wet.
The coolant looks ok and isnt low although could do with a top up! I have only seen the steam on odd occasions. Im guessing im safe? lol and im just getting paranoid!