:L im confused with the other answer- don't put the comma between which and was. Put it (instead) like this:
The moonlight reflected a silver glow off the empty road ,stretching out in front of us, which was still wet from a storm yesterday.
OR
The moonlight reflected a silver glow off the empty road stretching out in front of us, which was still wet from a storm yesterday.
you also might want to put THE storm yesterday...
You could also start a new sentence like this:
The moonlight reflected a silver glow off the empty road stretching out in front of us. It was still wet from a/the storm yesterday etc...