Virginia,

You'd think that at least the rain would clean the bike off as we rode, but no such luck! Not only does the bike get wet, but it is going to be covered with road grit. Bike parts do not like grit! When you get home, try to gently hose off all the grit. Put the bike inside where it can dry. I have occasionally used a blow-drier on low to get it dry more quickly. You will need to lube the chain every time it gets rained on. Rain washes off just about any lube, unless you are using some really heavy duty stuff and then your chain is constantly dirty.......
Also, pick up the bike. Shake it and listen......... do you hear water sloshing around inside? If so, not a good thing! Then you need to remove your seatpost and turn the bike upside and let it drain. It's pain to do, but it's worth it. ESPECIALLY if you have a steel bike.

annie