Weather Words: Thermal Belt

In mountainous locations, temperatures can vary greatly depending on the altitude, especially at night. Many times, cooler air will sink to the bottom of the mountains, leaving the valleys quite a bit cooler than the areas just above. This is many times referred to as cold air pooling.

This is also true to air higher in the mountains. As we climb higher in altitude, the air becomes less dense and pressure decreases. This causes the air to expand and cool through a process called adiabatic cooling. However, there is a sweet spot on the mountain, called the thermal belt or thermal zone, where temperatures are much warmer than the air both below and above it.

This warm zone is not only the Goldilocks of the mountain, but it has benefits for farmers. The milder climate that’s associated with the thermal belt results in a longer growing season for vegetation and allows farmers the ability to grow crops that might not survive the colder temperatures lower or higher up the mountain. The perfect example of this is vineyards.

In earlier centuries, settlers would seek out these locations to establish their villages, in hopes of searching for the temperature sweet spot.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.