Yes, it's most likely the belts, but doesn't indicate a problem per se. They do the same thing to me on occasion after rain or even after a cold night (because they contract in the latter case and are slippery in the first). I replaced my belts around 82K or so (more convenient to do so at the time I did it and also did the water pump).
Okay so i'm bringing this thread up because i'm having this problem. It just stormed insanely in missouri and my car was in the parking lot at work. I noticed today(a day later) that my engine is whistling, and i can tell it's the belt by the sound. Does it go away after a few days or so?
yeah its the belts. My mechanic fixed it on the spot in about a minute by tightening some bolts and now it hasn't done it for over 2 weeks. It used to every time it rained or even some light dew in the mornings. But even after a heavy down pour nothing