For me, this is warm enough in the 25*F and up range. I'm in CT and it has been a bit warmer, so I haven't tested them when it gets below 20. I have the sorpasso tights as well, and these are definitely warmer. The wind protection has been nice for the blustery cold fronts. So far, these are as warm as the pearl izumi elite amfib bib tights, but the castellis fit so nicely. I wear a small in all castelli wear, and these fit fine.
I'm 5'6 and 140lbs. My legs are considered muscular as well as my calves.