Wednesday was a day off, as work closed due to a forecast snow storm, but which turned out to be rain most of the day. I had imagined I'd have to shovel the shed clear to get the car in and out, as well as walk to and from there. However, there was no snow, only mud and water in low areas.
The road crews put some pretty nasty chemicals down before and during these events. It's a mixture of a liquid brine and salt crystals. You do not want either on your bike. There's a myth floating around that if you get it on there and leave it alone, dry, it will not harm your metal. I talked to a couple of body shop and automotive guys, and they both said that even dry, the road salts and brine will cause corrosion.
So what are you to do? I like to scope out parts of my ride on my way home from work. I can drive on these portions of road and check whether they've been treated, and if so, whether the treatment has washed away yet. A check today revealed some remaining salt and brine, but that it was largely cleared up. While I did not go for a ride, I think that perhaps tomorrow or this weekend I will be back on the road.
If you do get salt/brine on your bike, my advice is to use a damp, clean cloth and wash it off, then dry the bike carefully. Be sure to check "rust traps" like the insides of the fenders and around nuts/bolts/joints. If the road is particularly heavily treated, try an alternate route, or resort of a "beater" bike. This stuff is nasty.
The same here applies to salt water if you live near the ocean. You want to rinse and dry away salt water straight off. When I visited Chincoteague Island last summer, my nephews took their mountain bikes. The beach house's yard flooded with salt water at high tide, and they rode all through the salt water. By the third day all steel parts were rusted heavily and needed to be cleaned up.
So, the lesson I guess is to check the road conditions for salts/brine/etc and avoid if possible. If you do get some on the bike, rinse and clean as soon as feasible. Just because it's dried on does not mean it's safe for steel.