The lowest layer of the Earth's atmosphere, where most cloud formations and weather occur, is called the troposphere. The troposphere extends from the Earth's surface up to an average altitude of about 7-20 kilometers (4-12 miles) depending on the location. In the troposphere, temperature decreases with altitude, making it the region where most weather phenomena like clouds, storms, rain, and snow occur. It is also where airplanes typically fly and where the majority of Earth's air mass and water vapor are found.
