ashgarth,
I live in the cold and occasionally snowy not-so-flatlands of northeast Iowa.... pretty much the same weather/climate as you. I x-country ski, if possible, but snowy winters are few and far between, so you can't plan on this as a dependable option to riding. Snowshoeing is also a fantastic option, but the same limitations as x-c skiing - you need snow! And we don't always have that. I will do a bit of running, but since I HATE running, plus have a bad ankle, that's not my first choice.
I do a huge amount of hiking! We have some beautiful areas here, on or off trails. I think of it as cross-training and a needed break from the bike.
Much as I would prefer to be outside, I WILL ride my bike indoors on a trainer, just to be pedaling. I ride to music, but close my eyes most of the time and imagine myself on my favorite summer routes and try and get into a zone of riding. I wear a heart rate monitor so that I know what level I'm working at....... or I can get waaaaaaaaay to lazy!
You can join a club - do spin classes. Cross train. Lift weights. The main thing is to continue to be active.
Oh- did I mention cycling outside if there is no snow or ice on the roads?
With the right clothing, it is very do-able.
annie
Time is a companion that goes with us on a journey. It reminds us to cherish each moment, because it will never come again. What we leave behind is not as important as how we have lived." Captain Jean Luc Picard