Precipitation is generally low around 30 degrees north and south of the equator due to a phenomenon known as the Hadley Cell circulation. At the equator, warm air rises, and as it rises, it cools and can hold less moisture, leading to high levels of rainfall due to condensation. However, about 30 degrees latitude, this air has cooled and descends, creating a high-pressure system.
This descending air warms up as it gets closer to the surface and causes evaporation. Consequently, the air becomes drier, leading to arid conditions. This process contributes to the formation of desert regions, such as the Sahara in the north and the Namib in the south.
As a result, these latitudes experience clear skies, higher temperatures, and significantly lower precipitation compared to the equator, which is characterized by moist, rising air and plentiful rain.