A good, well balanced "Rain Gun" is a hunt saver. That's most especially true if you have to travel any real distance to hunt. Would certainly hate to fly or drive a thousand miles and then sit indoors, just because of rain. That's true for shotgun hunting as well as rifle hunting.
A Winchester Model 12 or a Browning Citori Featherlight can certainly fill the bill for upland hunting. Liberal spaying of a quality oil in the action (including removing the Citori stock) will keep things humming after a good drenching in the rain. They also swing surprisingly well. You'll also focus on the hunt rather than spending the day worrying about your shotgun.
Save the vintage English sidelock or Parker for the better days.