Fan belts usually squeal when they are loose or glazed over. Check and see if it is loose and tighten it if necessary. If it is tight and still squeals try getting some belt dressing for an auto parts store and spraying it on the belt.
Usually, it is your fan belt slipping due to moister. You can get a spray for it at your local auto store.
rub soap on the belt
Loose or glazed fan belt?
Could also be the belt tensioner ...
loose or glazed fan belt.
It sounds like the fan-belt is slipping.
depending on how low it is, it is either the fan rubbing against the casing or the belt that turns the fan coming loose.
You'll hear an annoying squeal. Maybe eventually the battery might die on you if the belt is slipping enough. Much of it depends on what the belt is actually driving which is probably more than the fan.
A loose or glazed "fan belt" is a very common cause of squealing. A quieter squeal is produced by brake linings that are almost worn through.
check tension on fan belt(s)
Thee fan belt is loose or dried out. Most likely loose.
A damaged radiator fan belt, or serpentine belt, shows signs of fraying, cracking, ribbing, and cording. Screeching or squealing sounds may also emit from the engine area, which indicates a need of immediate replacement or the belt may snap.