I haven't played it in a few months, but I think about Cities: Skylines [official site] every other day. I'm full of unresolved intent: to build new kinds of cities, dig further into the last expansion, to go hunting for new mods on the Steam Workshop. Perhaps the next expansion, Snowfall, will be when I make these goals a reality. We now know it's due for release on February 18th.
Snowfall is all about adding snow (!) to the game, but it's more than just a white texture layered upon the world. As mayor of your self-built city, you'll need to learn to do what English local councils cannot and deal with heavy snowfall. One of the developer diaries explains that this means hiring snow plows to keep traffic flowing, and that you can also pass new policies such as demanding "elderly people to wear anti-slipping studs on their shoes to increase their health." The simulation now takes temperature into effect too, causing houses to use more electricity and heating when blanketed by snow and requiring you to build new pipe systems to supply the demand.
Aside from the snow-related additions, the expansion also introduces trams to the game. These function similarly to buses, but you'll need to build them their own tracks and depots, of course. Given how much of Skylines appeal lies in its traffic simulation, that sounds surprisingly exciting to me.
I spoke just a moment ago as if layering a white texture over the world wouldn't be enough to appeal to me, but that's not wholly true. I'm looking forward as much as anything to the expansion changing the ambiance of my cities, much as I look forward to the shifting of the seasons in the real world.
The expansion will set you back $13 and though there's no GBP price yet, current exchange rate puts that around £9.
Here's the Snowfall announcement trailer, if you haven't seen it yet: