Mine does it in any weather
and it seems to be related to car jerking (when i press and release the accelerator in low gear it squeaks quite loudly) and when I pull off and sometimes when i change gear, to do with the slight jerk sometimes when changing gear. It doesn't do it when i rev not in gear so wouldn't hav thought it's the exhaust for me. But stops after driving for a while most of the time and also when i rains.