Radiational cooling is what happens on clear, calm nights when the ground loses heat straight back into space. During the day, the sun warms the earth’s surface — roads, fields, rooftops, and snowpack. But once the sun goes down, that heat doesn’t just disappear. It radiates upward, and if there are no clouds to trap it, it escapes easily into the atmosphere.
Here in the Four Corners, that effect is especially strong in our valleys and high basins. Cold air is heavier than warm air, so it sinks and pools in low spots overnight. That’s why places like Mancos, Cortez, and the high country around Rico and the Park Range can wake up much colder than the ridges above them on clear mornings like this.
The good news is, as clouds increase tonight and a warming trend builds later this week, that heat loss slows down. So while mornings stay chilly, daytime temperatures are expected to climb back above normal as we head toward midweek.
