Give it a wipe over with a pH balance wash product to remove any grime & help get rid of rain marks then dry it out slowly (likely to take several days if the knee rolls etc are drenched too). Then sparingly apply a good conditioner & if you are going to be riding in the rain regularly...
Best thing to do is give it a quick wipe over to remove any crusted dirt e.g. if you had been out hunting, then let it dry out slowly away from direct heat. This may take a couple of days if your saddle is really drenched.
Once your saddle is dry you need to replenish the oils that have been...