First thing to check will be the belt,sometimes they will stretch or get a hard glaze on them from the very hot temps.If it is tight then you can spray some belt dressing on it and that may help it,but if the noise comes back then you will need to replace the belt. OK

I checked the belts they all seem to be tight

First guess would be a slipping serpentine belt.

squealing is due to belts which have streached or become looser. The belt wraps around a drive pulley - eg alternator - and you need to find the adjustment bolt and lock to tighten the belt. While keeping the belt tight (by pushing on the unit it is driving) tightnen the bolt you loosened to streach the belt and any locking bolt .

Id bet anything on a slipping serpentine belt. Check the belt for tension (with the car turned off) if it is loose you will need a new tensioner. If it is still tight check the belt to make sure it isnt glazed over or damaged.

I have a 97 4runner for awhile it would squeal for a second on a cold start but now I notice it squeals longer and longer until the car warms up. But if the ac is off it doesn't make the noise at all any suggestions