For some reason, snow is on my mind lately. Since it's time for a weekend warrior* post, what can you do when, for whatever reason, you can't get out for your usual workout? The wrong thing is to do nothing. That way lies never getting out again. On the other hand, pretending that you can go ahead and do your usual workout is also not a good idea. Granted I could dress for a run in the current weather (near freezing, light winds). But I really can't run through 2-3 feet (50-100 cm) snow, and I'm absolutely not going to go running down the sort-of plowed parts of the road (with the cars taking uncertain aim at me -- folks here are not used to driving on snow, and there's almost nothing you can do about the ice that is increasingly common).
So, what to do? Well, first off, prehabilitation exercises are a good idea.
More generally, if health is your aim for your exercising, do anything that is good for your health. Maybe this means visiting Pubmed and finding out more about what a good diet is, or what good exercises are. Since this is a research-oriented site, it'll be tougher going than many. Still, being a research site, you'll be able to see the original scientific claims -- vs. the drastic and dramatic things you might see in your local media outlets.
A related option is to look up more about what kinds of things you should be eating. Again, I like pubmed or webmd -- places closer to the research. Your snowed-in time could be a chance to get hold of some recipes to cook up things you know you should be eating, but have never liked much. (I've lately discovered that spinach can be ok -- just not if done in the way I grew up with. Salads are ok.)
It's also a good time to do the strength work that you know you should be doing, but don't normally do because you're out swimming/running/biking/... instead. Strength does matter. And it matters more the older you get. In my physical therapy, it's developed that I also have a particularly weak right hip. Much more so than the left. And it's the right calf that has the problems. These two facts are probably not unrelated. What it means is that to rehabilitate my right achilles+calf, I have to do work on my right hip. We've also discovered (no surprise, I've been very 'right-legged') that my left quadriceps is much weaker than the right. So I have to work on strengthening the left quad. And the right everything else (which surprised me -- the only thing on my right side that is stronger is the quadriceps).
Lest you be concerned about bulging muscles or the like, no worries. Strength is a fairly different matter from building big muscles. And I'm not referring to building olympic-class strength. But getting strength around your body, so that all muscles and muscle groups are easily up to the tasks of doing the other things you like (running around with your kids/grandkids/..., or walking around the woods looking at birds, or ...), is a big plus. And it is distressingly easy (see my hip exercises above) to be in a position that you are doing a lot of compensation for a week muscle here by making some other muscle work too hard. That works for a time, until the muscle that's making up for the weak one decides to give up. Or, where I found it first, some other muscle gives up and gets injured. Get everything in to good condition and strength.
Related to the strength work is flexibility. Your muscles are strongest when they have a full range of motion. (Again, I know this because I have some extremely inflexible muscles. And I've been working on them. I'm looking forward to finally getting back out and giving a try at some real speed.) So if you can't get out for your workout, do a good set of stretching exercises. Pay particular attention to your tightest muscles.
* I'm not sure how widespread this term is. Weekend warrior means the people who are at a desk job 5 days a week, and then go out on the weekend and act as if they're at least at the Olympic trials, if not the Olympics themselves. Tend to be noticeable on Monday as they're the ones limping down the hall.