Aquariums and indoor gardening can be fun in winter! Both can grow plants. Get some white grow lights and a cabinet and they work quite well.
Larger aquariums appear to be easier to manage than small ones, if you pick that up. Things happen more slowly in larger aquariums since things are more diluted.
Skiing is really fun in winter, downhill mountain biking in summer is awesome. Getting your $35 GMRS license allows you to use the more powerful walkie talkies, which are nice for skiing and biking, but also have entire communities of their own, when I switched on my mountain radio in town and accidentally found a group doing radio-based trivia on an island 30 miles south of me. Kinda neat!