2002 S-10 4.3L wont start when wet

My 2002 S-10 has a 4.3L vortec engine, 75k miles. 2 times now I have tried to start it cold when it was raining. The engine sputters for a few seconds but will not start, then just cranks with no fire. First time this happened I left it for 8 hours while at work, tried it when I got home and it started no problem. 1-2 months later same deal, rainy night and the truck wouldn't start, walked home and got back to it next day, started no problem. Runs well when running and will usually start when wet.