clutch comes and goes

I own a '93 Wrangler with a straight six high output engine. My clutch is giving me problems lately. It seems that when it is raining, I loose the clutch, and the pedal goes through to the floor. I do not loose any fluide that I can see. After driving 200 miles on the highway and nursing the jeep home without any clutch what so ever, I checked it 2 days later, and it was fine. Rode it the hole week with no problems. But it was't raining. I had the clutch bled once before appr. 2 month ago, and that seemed to work at the time, but now it is happening again.
I had a new Clutch and slave put in last year in summer, the lines and master are still original. Any input helps.
Thanks

Take it back to the shop that changed your clutch, have them adjust it.