I'm not sure most people realize how cold it can get in that area at night, still, cloudless nights with great radiational cooling.
True. When many people think of "Colorado weather", they think of Denver. Much of Colorado is actually much colder than Denver. I actually have a book somewhere at home that says snow doesn't stay more than a few weeks below 7000 feet in Colorado. Places like Steamboat Springs and Craig are below 7000 feet, but the snow here has stayed on the ground until April or May in every year but one (2007), where the last of it melted on March 31.
Anyway, -8F (-22.2C) this morning. I don't think it will drop below zero tonight or even get close. It's snowing right now and is supposed to remain cloudy all night.