Have you ever noticed how valleys and low-lying areas feel colder on calm, clear nights? This phenomenon is known as cold air pooling. As the sun sets and the ground releases heat, the air near the surface cools and denser cool air sinks into lower elevations, such as valleys and basins. This can lead to fog settling in these areas and create significant temperature variations over short distances. While higher terrain remains relatively mild, low-lying spots can become much colder, sometimes causing frost to form, even when nearby areas are above freezing. Cold air pooling is most common on windless nights when the heavier air settles in place.
Meteorologists closely monitor cold air pooling, especially during growing seasons when unexpected frosts can harm crops. It also impacts air quality, as pollutants can be trapped in these pockets of dense air, leading to poor visibility and smog. Whether causing a morning chill or influencing local weather patterns, cold air pooling is a subtle yet impactful force in atmospheric science.
Jennifer Gray is a weather and climate writer for weather.com, with over two decades of experience covering major weather and climate events worldwide.
