91 hijet does not like humidity

Hey guys, my 91 hijet either wont start or will take a lot for it to on days with high humidity. If it does start it will always backfire before. Any idea what causes this? Thanks!

 

Are you getting moister in the distributor cap?

 

Not too sure, havent looked too much into it. First issue i've had and unsure of where to start

 

Check to see if the cap is cracked or maybe not tightened all the way

 

I agree on the cap