I've had a similar problem with my wife's Subaru Forester.
She came home on a Friday night after work. The weather was great and she had had the roof open and forgot to close it when she came into the house. Well, it started raining later that night and dumped buckets all weekend long.
Monday I need to take her car for the day for some reason. I go out to the car and see the roof open and dread looking inside. I opened up the door and see over an inch of water standing on the floor and the cup holders are filled to the rim. Suffice it to say I was NOT happy.
I ended up soaking up the water with towels and driving to work sitting on a trash bag. When I got to work I left all the windows open along with the roof and mother nature did the rest. Completely dry for the ride home.
The car has never acted funny, runs like a top, never presented a problem (knocking madly on wood here
) since then and it has been well over a year since its "bath".
I don't have my H3 yet so I can't really comment much on that, but my guess is that your H3 will be just fine. Its a HUMMER after all, its got to be tougher than a wee Subaru.
Rob (Ipedog)