@Trilby: In Minnesota, the weather has been known to occasionally cycle from the mid 80s straight down to below freezing in about 3 hours... Last time, it happened during the middle of duck hunting season, and was accompanied by a huge fucking blizzard.
Also, since the weather changes so quickly here, I don't watch the forecast, and have learned to live with being rained on. I've gotten fairly good at telling when it could storm...