On a rainy camping/photography trip, I heard one of the other photography enthusiasts quip that "Bad weather equals good photos"
It appears that that sentiment is echoed by others.
Here's a quick tips & tricks page at the National Geographic by Jim Richardson, on how to get the best out of wet weather photography.
I found some of it quite interesting. Especially on the use of flash, which I was told was normally a no-no in the rain, but apparently not necessarily so if you do it right.