You're sick of running on the treadmill everyday. The roads are actually clear of snow and ice. You are itching to break out your tighty, running tights and breath in the brisk cool winter air. And then you look out the window and there it is. The Salt Lake Valley winter smog. You've heard running in it is like smoking a pack of cigarettes. True or not you'd rather not find out.
City Creek Canyon is the answer to your winter smog running blues. The smog is usually brought on by the infamous "inversion". I can't tell you all the scientific reasoning, but during this time, City Creek Canyon stays free and clear of the smog.
I've run there in the winter and it's even been warmer the further up the canyon I went. Except for immediately after a snowstorm, the roads are kept pretty clear even in January and February. There may be a few ice patches where the water runs across the road. Just be smart and slow down to an awkward shuffle.
This is actually one of the most beautiful routes I've run in the winter. Blue skies, snow flocked evergreens, and the sound of City Creek babbling down the canyon.