Like BJ said, give it a few days. If it was a heavy rain, the moisture laying on the paint film usually dulls the gloss of an oil based finish. If it was a brief shower, you may luck out and only get a few "fish eyes" in the finish. I can remember the old days when oil took DAYS to dry..........any kind of moisture could set you back........did some aluminum siding.......got a heavy September fog and the paint literally SLID off the siding! Not good.