Weather has no effect on timing. I'm inclined to think your problem is more along the lines of wet weather. Condensation inside the distributor or a bad wire, etc.
Also, don't listen to the Q-jet nay sayers. They have no idea what they are talking about. When someone tells you to ditch a Q-jet and stick a Holley on something, this tells me real quick they are clueless what a good carb really is.
