It was 16 degrees when I left this morning, my brakes (canti's) ground on the rims like bricks until they warmed up. I think the pad material simply gets cold and brittle in this weather, that said, I've ridden in temps as low as -1 degree and the brakes still worked. I would recommend riding them periodically to warm them up prior to really needing them (like on my descent into the parking garage, it's a steep hill followed by a sharp left).