My 03 blazer will not start in extremely damp and wet weather. Any ideas?

I keep it in the garage. If I go to the store after a day or extremely wet weather, the car will not start when I come out. I have even put a starter fluid in the carburetor and the car starts and only runs until the fluid has been used up. It seems that it is not getting gas but how can this be affected by the high humidity in the air?