One answer is some kind of cross training.
What I worry about is weather as bad as we had it last year with two feet of snow that stayed around for weeks. I live "in the DC area" but more specifically, I live in the outer fringes of the suburbs where the roads aren't as well taken care of as they are closer in to the city - and those city roads weren't taken care of very well anyway! And our roads out here have no shoulders and we have no bike paths so I have to share the roads with the traffic. Normally not bad unless I'm on a back road where it has been plowed to only about a lane-and-a-half wide ...
Yeah, but that certainly isn't typical of the area. Odds of having another year like last year any time soon are pretty slim.
That said I usually just trail run rather than ride most of the time when not on tour. Possible options for when there is 2+ feet of snow on the ground are XC skiing, running in the tire tracks on back roads, and snow shoeing. Last year we got 50" in the same week and I didn't miss a run, but did have to run on roads rather than trails some of the time. This year I plan to snow shoe if we get large amounts of snow.
Besides ... haven't you ever looked out the window when it's 35 degrees and drizzly and just said "nah ... no riding today"?
Yes, but that is great trail running weather, so I just go for a run.
When I have (very rarely these days) used some kind of indoor trainer (usually rollers or a rowing machine) I just put on a movie or caught up on some taped or DVR'ed TV.