My Worksman cruiser has the old Ashtabula-type bottom bracket, hubs, etc. It seems like every time I've ridden it in the rain, it magically has the bearings loosened up the next day or two. I don't know if grease gets washed out, or if things get a bit of rust that then wears off, or if being wet lets a nut back off that wouldn't otherwise, but it seems to be more than coincidence. More modern stuff may not do that.
__________________
"be careful this rando stuff is addictive and dan's the 'pusher'."