I have friends who wear those disposable gloves UNDER regular short cycling gloves for doubles and longer rides where the start is REALLY cold, and then it warms up. I did that for the Death Ride and it was terrible! My hands were soaking in a pool of sweat by the time I took those off (at the FIRST pee stop I made on the first part of Monitor!) I took the gloves off and about 2 T of sweat poured out of them! I never knew my hands sweat so much.

I ride in the rain a lot, and don't use waterproof gloves. Just use long fingered gloves and you should be fine. You may get wet, but the key is to stay warm.