The accessories on the engine cause alot of torque to be placed on the belt. When you first start the car the device whos belt is loose wont be up to speed and the belt spins causing it to squeal. Same thing if you are at a stop sign and step on the gas to go. The engine speeds up but the devise has to catch up. This is usually a quick fix and one person can do it. Some cars have a belt tensioner built in and it only takes a few turns to fix it. Others require a little longer but I havnt found a hard one yet.
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.
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.
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.
Usually, it is your fan belt slipping due to moister. You can get a spray for it at your local auto store.
check tension on fan belt(s)
Thee fan belt is loose or dried out. Most likely loose.