Damn! It's cold. Like Steve, with the recent string of cold mornings, anything in positive double digits is a heatwave, despite what Pharmie says. Despite what the temperature says, one must toughen up and just run. (Some people even bike, but that's just crazy.)
It's been said that it isn't too cold to be outside, you're just improperly clothed. Which I'm quickly finding out to be an important point. On Sunday, the home thermometer said +12°F but sunny. I put on my warm tights, thick socks, a short sleeve, long sleeve, and a thick long sleeve outer layer for my one hour, fifteen minute run. I was fine for the first 55 minutes, and then the sun went behind the buildings and then the horizon. My all-black outfit had kept me toasty-oasty warm, but without the sun, the wind picked up and I got cold - fast. The sweat from my belly now wicked the wind and my skin started to freeze. The exposed skin around my neck and cheeks burned. I was cold and tired, but nearly home. I toughed it out, and checked the damage at home. My belly was all red where it pressed against my shirts. It lightened up after two days, but I could tell I suffered from frostbite.
Tonight's run was better. Same temp, but it was without the sun's warmth. Also, it was shorter at a faster pace, so I was able to keep the furnace going and stayed warmer. The big difference was the length of exposure. In future runs, I need to consider the length of the run into my clothing choice. The longer the run, the thicker the layers need to be.
Remember, it's not the temperature, but the protection!