I have a 2001 Toyota Echo. It squeals, really loudly. It squeals regardless of the weather and regardless of how long we’ve been driving. It only stops squealing when we accelerate the car to ~40mph or so. Then it stays quiet until we begin decelerating. Sometimes we can prevent it from squealing by turning the fan/AC/heat off before we decelerate.
Sounds like a bad drive belt. If you have a serpentine belt then replace it after checking to see if it’s properly tightened and tensioned.