I use Sport Hill XC pants. Originally a winter cross-country ski pant. I use these with no base layer down to 25f/-3c. Below that I wear either workpants as baselayer or cycling tights. windproof and coldproof. expensive but will last years. I have had mine going on eight years now, and still going strong. below 20f/-6c I will add leg warmers for extra warmth. That works down to -5f/-20c.