I went today. It was good fun despite the rain. As long as we were moving, it wasn't too cold, so we just didn't stop (except where the traffic bottlenecks forced us to.)
At the last stretch the marshals were directing us around massive puddles; we rode through them intentionally, it simply wasn't possible to get more wet at a point where your shoes are essentially personal swimming pools for your socks.
The ferry ride wasn't bad on the lower deck, but getting back out into the cold again was horrid. We decided to just ride back instead of taking the subway.