1999 Dodge Avenger squealing belts in the Morning

On cold, damp or heavy dew or frost days, when I start my car one of my belts starts to squeal loudly. I have my defrost on someitmes and have turned it off and the squeal usually stops but now two days later on a cold and heavy dew morning, once I started to drive and then stop and start to drive again is starts to squeal loud again. I had always heard that was a 'timing' belt squealing. It does stop and it doesn't do it during the day, just first thing in the mornings. What is it? What needs to be repaired? Is it hurting anything? Also these are probably original belts anyway!