All weather occurs in the troposphere layer of the atmosphere. The troposphere is the lowest layer of the atmosphere, covering approximately the first 6.8 miles from the ground.
There are five layers of the atmosphere in total: troposphere, mesosphere, stratosphere, thermosphere and exosphere. Each layer is of varying size, and is defined by unique characteristics.
The troposphere is known for containing almost all the water and aerosol chemicals in the entire atmosphere, despite being the smallest layer. Additionally, this property is the main reason that the troposphere composes about 75 percent of the atmosphere's total mass. These conditions are necessary for weather (rain, snow and more) to form.