This is my everyday running vest. I live in Colorado, and so far it's provided just enough insulation for weather in the low teens (with a couple of lighter thermal layers underneath) without being cumbersome. I would suggest something heavier if you're running with cold AND wind.

The only reason I gave this vest 4 stars and not 5 is because the zippers are a little 'fragile'. They can get stuck and have split apart when things are not lined up correctly; however, there haven't been any permanent issues. I can usually unzip and rezip and the problem is fixed. For the price and quality, I'd buy it again!