How cold is it at 20,000 feet?

This holds true up to 36,000 feet msl. So, while your standard temperature at msl is 15° C or 59° F, your standard temperature at 20,000 feet msl will be -24.6°C or -12.3°F.



At an altitude of 20,000 feet, the air temperature is significantly colder than at sea level due to the standard lapse rate of the atmosphere. In a "Standard Atmosphere," the temperature drops by approximately 2°C (3.6°F) for every 1,000 feet of ascent. If the temperature at sea level is a mild 15°C (59°F), the temperature at 20,000 feet would plummet to roughly -25°C (-13°F). This extreme cold is a primary reason why aircraft cabins must be pressurized and climate-controlled to keep passengers safe and comfortable. At this height, the air is not only freezing but also contains much less oxygen, making it an "unfriendly" environment for human survival without specialized equipment. For mountain climbers tackling high-altitude peaks or pilots in unpressurized cockpits, this level of cold requires heavy thermal protection to prevent frostbite and hypothermia within minutes. Furthermore, these freezing temperatures at 20,000 feet are responsible for the formation of cirrus clouds, which are composed entirely of ice crystals rather than water droplets.

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The reason commercial airplanes fly at 30,000 to 36,000 feet is because it places them in a unique part of Earth's atmosphere known as the lower stratosphere. The lower stratosphere is above the clouds, so commercial airplanes are protected against bad weather.

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Air itself is constantly in motion; it will often rise toward the sky. But, any air that rises will expand and cool, as it encounters progressively lower atmospheric pressure (explained further in the next section). The upshot is that the air outside a plane will be much colder than at ground level.

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On average, you will find most commercial airliners flying anywhere from about 31,000 feet to 42,000 feet. That is equivalent to 5.9 to 7.2 miles in the air. Smaller aircraft, whether commercially operated or not, will fly at lower altitudes, often below 15,000 feet.

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When a plane flies through a supercooled cloud the disturbance causes droplets to collect on the airplane, and since the water droplets are already supercooled they solidify into ice almost instantly. While flying through a large cloud of supercooled water droplets, an airplane can experience considerable ice buildup.

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The outside air temperature on a flight at 30,000 feet regularly reach temperatures as low as -80C, or even -100C without any problems. Aircraft are designed to cope with all weather extremes and the speed and movement keeps the temperature in the engines and fuel tank much higher than the outside temperature.

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At 40,000 feet its only 2.72 PSI. If outside air gets into the mask and is breathed, it contains one-fifth (20 percent) of the oxygen necessary for survival at 40,000 feet. The time of useful consciousness on ambient air only at 40,000 feet is 15 to 20 seconds.

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Planes have lower oxygen levels If this didn't happen, everyone inside the plane would die, as the low air pressure at the elevations planes fly (typically 35,000 feet or so) means there isn't enough oxygen present for your body to function.

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Your body would take between 18-36 hours to freeze in space due to the radiational cooling. There are other problems when it comes to being stranded in space though. While freezing is not your most immediate concern, oxygen and extreme low pressure are things to be concerned about.

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Without air in your lungs, blood will stop sending oxygen to your brain. You'll pass out after about 15 seconds. 90 seconds after exposure, you'll die from asphyxiation. It's also very cold in space.

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