Well, the weather is a problem, but maybe you could make the problem work in your own interest. That’s parkour, which is much as marcial arts and more disciplines that teach you how to see the world in a different way. A way where everything is connected and makes sense, so you can always turn “bad things” into just things. And overcome them or use them in your best.
I will better explain myself…

If you like parkour, but you don’t know the basics and you just know what you have seen in movies, you probably will try to start doing things you are prepared to.
That’s normal. And it’s normal in any activity. But here could be dangerous or slow you down in your progress.
So, as you can’t doing big jumps from roof to roof or running jumping through your city, you will have more time to learn well the basics techniques and teach your body how to do things.
The bad side is that is more much fun to jump and run free, but if you are patient and practice until the weather be good enough, you’ll probably improve faster and safer.
I would start improving my balance and precision. It’s easy to practise anywhere, even indoor.
I think in the link I post are doc about the different basics moves.

But probably there are local group on your town (or near by). I didn’t know that here were a group and actually, I think there is more than one.

If you want examples of exercises or so to start, I like to post some of the training I’m following.

Cool stuff. I really like to start practicing parkour too, but I have no idea where to start from. And the weather is so bad here that I prolly have no choice other than thinking about it again in the Spring.

Cheers,
behdad