Replace the tensioner. Stop it from getting wet by making some sort of shield to prevent water from getting to the belt.
it could be a serpentine belt or accessory belt.
Change the belt
Check you serpentine drive belt and pulleys.
Water from the road has splashed up into the engine serpentine belt causing belt slippage that makes a squealing noise. The sqealing is one of your engine assessories that use the serpentine belt to drive it.
serpentine belt loose
A worn belt will cause a squealing noise. The squealing noise is caused when the belt slips. Tightening the belt will temporarily fix the problem.
Worn serpentine belt and/or belt tensioner.
Either it's too loose or you need a new belt.
sounds like you need to replace the serpentine belt
Possibly the wrong belt was installed or most likely your belt tensioner is bad.
Your serpentine belt is loose or worn.
It Could Be Your Serpentine Belt too tight or not tight enough.