Screaming noise in Volvo XC70

We have had a 2004 Volvo XC70 for two years now, problem-free. But recently we experienced a strange, new thing. We were driving in a very heavy rain in Maine (during the hurricane) and suddenly the engine began screaming…not at all like a loose belt or bad bearing, but really loud, seeming from right front. We stopped, no idots lights came on. Began again, soon the same thing. Stopped again, waited, then took off again, with rain lessening. No further problems the rest of the drive back to Vermont. But now, we occasionally have the screaming, only briefly and ONLY when it rains. It concerns us a bit, and our mechanic has no idea. Any ideas on what gives? Thanks for any help out there. Charles

Try a new serpentine belt.

And when it gets a new belt someone should check all of the pulleys and check the splash shields under the car to make sure they’re intact.

After belts etc. you should check the position of the resonator against the drive shaft, there are reports of water or slush on the exhaust run causing it to push against the drive shaft causing a squealing. If that is happening you will see a wear ring on the drive shaft where it rubs against the resonator.