What are you running now? Because this seems like exactly the thing a ThermoQuad was designed to prevent.
Also: what altitude are you at? High altitude makes all that worse.
I have had good luck on carbs (motorcycles) using StarTron and StaBil for ethanol.
Something is very wrong, because it gets REALLY humid here about 9 months of the year. I thought most of Idaho was high desert!
I'm in New England (humid) and had no heated storage.