Holy crap!
I was stuck in a very large downpour on my commute home.
The cherry creek trail started to flood. Riding through a foot of rain water is quite disconcerting.
The next time this happens I am diverting to street level. Better slow than drowned. The cherry creek runs between the East and Westbound lanes of a busy street and is 20 feet below street level. Storm drains also dump into it.
I almost did something stupid while trying to reach my destination before the creek flooded. I was in my drops going about 24mph during the rainstorm. A group of people were clustered under an overpass and one of them stepped into my path. 162lb rider+30 lb bike +10 lb of gear going way too fast in a rainstorm would not have been a nice collision. Fortunately, when I yelled he jumped back and proceeded to mouth off. To which I mouthed off right back.
Anyhow, that scared the crap out of me.
In summary:
1) don't ride in a rainstorm in an area prone to flooding
2) ride an appropriate speed in said rainstorm.

stupid stupid stupid
Well, it didn't turn out bad.