This purchase was actually a gift for my brother who recently moved to Montana. My husband and I discovered Smart Wool for our ice climbing trip in Colorado, and we are customers for life now. Born and raised in Texas, being cold does not come easy for us, so we wanted to be prepared. We spent two days on the mountain in February and these base layers saved our lives! I couldn't believe how "comfortable" you can be in single digit temps in the snow and ice! We even wore them throughout our Texas winter last year (which was one of our coldest) and now we swear by them!
The nights are still chilly, but that's the only time I have to run these days. These things keep my lower anatomy warm and secure, which is how I like it. Not to mention getting a free pair of SmartWool socks with them thru a Moosejaw Promo! I think I can keep running until the weather makes up its mind of what it wants to do.
I'm sold on merino wool and wear Smartwool from head to toe as my baselayer. This bottom layer wicks sweat better and is warmer than synthetic, and doesn't smell as bad after 2 weeks of wearing. I prefer the lightweight over heavier options as it functions in a much wider range of temperatures without overheating me.