I think you may hearing/feeling a dry chain. It won't squeak or make that classic "hedge full of sparrows" sound if it's drenched in water, but it can feel sort of grindy.
Unfortunately rain here usually means low temperatures. If I have to ride in the rain I try to make sure to dry my bike out quite fast, by taking it inside somewhere warm and dry. When dry I relube the chain with a heavy oil, and let sit until the next use. I leave a rag hanging over the rear triangle, to remind me to wipe off the excess oil before I take the bike out again.
Other parts of the bike can get the oil washed out too, but the chain is by far the most exposed. I've routed my rear brake cable through a housing that goes the full length of the bike, zip-tied to the fram, to minimize exposure, seems to help. I've also lengthened my front fender with half a plastic bottle+zipties, which helps to protect the bottom bracket.
I think most bikes can handle rain quite well if they're allowed to dry quickly and re-lubed regularly, but the mud and sand that the rain can bring with it is worse.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett