For below 40f. I wear Sporthill XC pants. I wear them with just underwear down to about 15f. Totally windproof and coldproof. They're expensive. But you can find them on sale on the internet. This is my third year with them. And they're built to last. IMO the best winter cycling tight out there, even though they were originally designed for cross-country skiing. Sporthill makes excellent winter gear.