No heat in cold/humid weather

Since 2004 the heater in our 2003 Element has not worked when the weather is in the 40’s or low 50’s and it is raining or humid out. If it’s dry out - the heater works in those temps. It always works above and below those temps regardless of humidity. I never brought it in because I thought they’d think I was crazy. After 6 years of this - I’m tired of being cold. I can’t find a problem though. Any ideas?

The best idea would have been to bring it in while it was still under warranty. I suspect there is no warranty now.

Do you have one of those fancy computer controlled systems with different temps for the driver and passenger side?