Sounds to me like you got a bad radiator fan bearing. Bring it to a mechanic. It may need to be replaced or simply just re packed with grease. If you know auto mechanics you can do this yourself. Invest $25 at your local auto parts store in a haynes manual. Trust me their life savers.
Pop the hood and see if the squeel is coming from the belt, maybe the belt is worn and slipping on the AC compressor. OR the AC compressor may be going bad and causing the belt to slip over it causing a squeel.