Semiconductors are happy with higher temperatures, but resistor values can drift at higher temperatures, and you risk drying out electrolytic capacitors if they get too warm.
You don't absolutely need to bake out the circuit board, so long as you're very patient and certain the the water wicked up under various components is fully evaporated before you turn it on. If you don't bake it, I would let it sit for several days, rather than a few hours. Water doesn't easily come out of some trimmer resistors, for example. (On the bright side, though, it's also harder to get the water *into* them, too.)