D90 stands up to humidity?

I have taken mine to the rain forest in Costa Rica with no problems.

The comments (elsewhere in the thread) on silica gel are always a good idea.

I'd try to keep it away from air conditioning, if you can. The a/c tends to be cold & dry and as soon as you take the camera out on the a/c'd environment it will immediately get condensation forming in it & on it - not a great idea!