I ride right through winter here in Ontario, no problem. Even the days we get below zero/freezing, I'm out there. But I have a complaint: when it gets down to -5 my quads get chilled. I'm good at freezing, I'm good at -1, and I'm good at -3, but when it hits -5 or below my quads get cold.
Here's what I wear on my lower half: a pair of tights, a pair of leg warmers over top, and then my bib shorts. That's it. Basically I've got three thin layers of spandex over them, and once the temps drop to 5 degrees below freezing by quads get chilly. Funny, my knees and everything below them are fine, it's just my quads.