Everytime it rains I go out to start my Blazers it doesn't want to start I'm assuming there's moisture getting into the distributor underneath the cap has anyone had this problem and if so how how did you fix it? Thanks in advance for any help

 

There are too many possibilities. The Blazers are not commonly known to get moisture into the distributor. If so it may already be corroded internally.
If the truck is parked under trees the gutter like edge under and around the hood can overflow and water seep into the engine wiring and as well the distributor.
Contributing is normally a missing joint along the u-profiled edge on the firewall side.

Would need to look where water enters the engine bay. Still other possible places that can get wet and cause a non-start.
Also check distributor cap itself if cracked.