The uneven heating of the earth’s surface from the sun is a primary factor in atmospheric circulation.
The atmosphere is in constant motion. This movement is the key factor of the various weather conditions. The uneven heating from the sun causes some areas to be warmer than others. As air warms, it ascends leading to low pressure at the surface. As air cools, it descends leading to high pressure at the surface.
FAA AC 00-6B Aviation Weather pg. 4-1
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 12-3