I'm sure this is a dumb question, but I'm heading out of town to a duathlon this weekend and not only do we have to drive with the bikes in the rain (on the bike rack) but we were planning on leaving them in transition tonight (security provided) but now it looks like it's going to rain on and off all night. WOuld you be concerned about anything? Should we get up extra early to get the bikes into transition in the morning instead?
It sounds like you are concerned, what about? I'm sure your bike's been wet before, right? And you know and can trust it still works, right?
I would do everything per usual, except in the morning before the race starts dry off your saddle, your pedals so you don't slip trying to clip in, and if you can, your braking surface on your wheels. Most races I have encountered that provide overnight security for bikes in transition, require that you rack your bike the night before, so it's not like not doing it is much of an option. If it IS an option you could wait til morning to rack it, but where would you keep the (wet/dirty from driving) bike overnight?
All in all a little rain doesn't bother me too much.