As Resident said. Dark cold winters. However it's only for 2.5 maybe 3 months. The cold is a very dry cold so you get used to it fairly quickly and if you dress warm it's not a big deal. There's not a lot of snow fall (at least compared to when I lived in central BC), but its there all winter. We even got a big dump (~5" in mid May this year).
Come March it starts getting light very quickly. Come May it's light out until 10:30/11. Mid June it's light all day long. According to the weather network sunset tonight is 11:35, and the sky will still be light out until 130/2ish.
I buy a lot of things online or when I make regular trips south. But we have a Walmart, Super Store and a large Canadian Tire. Between these places you can usually find the 'normal' things you're looking for.
Other than housing and gas (at least compared to you guys in the US), I don't really find much of a difference up here compared to down south. We don't have the selection, but it's not too bad. Nightlife kinda blows, but its all about what you make of it. With the right group of friends, you can still go out all night and have a blast.
Whitehorse is about 26k in size. Situated in a valley surrounded by mountains/big hills. I can be kayaking on 7-8 different lakes, or the river within 30/40 minutes of leaving my house. 20 if I go to one of the several close ones, and I live right in town. It's about 40 minutes to get to the top of 3 of the hills/mountains surrounding town. Most little cars could make it up there (well probably).
The big thing is just the housing. It's fairly pricey - even just to rent. Most 2-3 bedroom condos go for 1200-1500 plus utilities (heat,electric/tv/internet/pho ne). I own a condo that I rent and when I first listed it this winter at 1500 I had 20+ emails within 3 days. So if you do come up here, line up a place to stay before hand. Even if you're going to be in a hotel (many are full all summer long). I don't want to scare you off, but it is what it is. If you look in advance it's not a big deal to find a place... you're just going to have to pay for it.
It's also a very spread out town. End to end along the highway is probably 35+km (city limit to city limit). The transit system blows, so a vehicle is almost a must. You can make do without, but it's a major pain if you want to go outside the city center. Winters without a car would also blow.
I came up here in 2000 and hated the first year or so. Now 12 yrs later, I doubt I'll ever leave. It's very laid back, and people are very easy going.
As for Canada's political landscape, it's very Liberal (much to my dismay). The conservatives in Canada are further left than the US Democrats. Yukon is probably one of the more conservative places, yet there's still tons of hippies and Liberals. And we're all polite enough that we all still drink beer together.
The only other northern place I've been (of any size) is Yellowknife (for work). There is absolutely no comparison. I don't mind going for a short stint (a week), but would never ever live there. Housing is more expensive, and it's flat. Like perfectly flat. There's no hills, mountains or anything. Their ski hill is down into an old mine pit. Maybe that's okay with you, but it drove me nuts. It's also a very transient place. People come up, work & make money then leave. Here they tend to stay a lot longer. I also found it a dingyer town. And one that's very very compact. You can walk or bike everywhere (if you wish). Whitehorse you can... but depending on where you're going it could take a bit... Whitehorse also has the advantage of being able to drive out (north, to Alaska (Skagway is 2 hrs), east, or south). The road pretty much ends in Yellowknife. I found this to be a kind big deal. When you need a break... go for a drive to check out other places. An hour south, or 30 mins north and you're suddenly in the middle of nowhere. Nice, peaceful and quiet with tons of fresh air... just how I like it. Hope that helps. JR