Why Is It Colder at the Top of a Mountain Than It Is at Sea Level?

By: HowStuffWorks.com Contributors  | 
Lower pressure at higher altitudes causes the temperature to be colder on top of a mountain than at sea level. Pictured is Mount Everest behind the mountain of Nuptse. Education Images/UIG via Getty Images

You may already know about the relationship between temperature and pressure: When you pressurize air (or any gas), it gets hotter, and when you release the pressure on air it gets colder. So a bicycle pump gets hot when you pump up a tire, and a spray paint can or a C02 cartridge gets cold as you release the pressurized gas. A refrigerator puts both of these processes together, pressurizing gas on the outside of the refrigerator to release heat and decompressing it inside the refrigerator to absorb heat (see How Refrigerators Work for details).

You may also know that air pressure decreases as altitude increases. This table shows the pressure (in pounds per square inch) at different altitudes:


Altitude and Air Pressure
Altitude and Air Pressure
HowStuffWorks 2018

As air rises, the pressure decreases. It is this lower pressure at higher altitudes that causes the temperature to be colder on top of a mountain than at sea level.

For more information on related topics, try the links on the next page. 


Air Pressure FAQ

What is air pressure?
Air pressure can best be described as the weight of the air molecules that press down on the Earth. The air pressure lowers as altitude increases. Therefore, the highest air pressure is at sea level where the density of the air molecules is the greatest.
What is the normal atmospheric pressure?
The standard or close-to-average atmospheric pressure at sea level is about 14.7 pounds per square inch. However, the atmospheric pressure does not always equal this standard value due to changes in the weather.
What is considered high air pressure?
A barometer reading of 30 inches (Hg) is considered normal air pressure. Similarly, a reading of 30.70 inches is considered high air pressure. If the air pressure falls below 27.30 inches, it’s considered low.
How does air pressure affect us?
Air pressure is the weight of the atmosphere around us. It affects us in different ways. For example, low air pressure puts more pressure on the joints and can exacerbate pain. It’s also a common culprit or headaches and migraines, a drop in blood pressure and increased sinus pressure.
What kind of weather is associated with low air pressure?
Low air pressure is associated with high winds, precipitation, cloudy weather, and tropical storms.