1999 Chevy Silverado back windows

OK, silly question, but are the window "Lock cams" pushed into the locked position? If so, the rubber weather stripping is worn/deteriorated. You can either replace the weather stripping or you can try a thin strip of adhesive (house door) weather strip material on the contact surface(s). Any hardware store will carry that stuff.

My truck has wind noise but it is not from the rear windows, it is from the driver's side door. The door hinges will sag and allow wind to pass between the metal door skin and the rubber weather stripping material.