How are deserts formed?

Deserts are formed due to a combination of climatic and geographical factors that result in low precipitation, typically less than 250 millimetres (10 inches) annually. Some deserts, like the Sahara, form in regions with high-pressure systems that inhibit cloud formation. Others, like the Atacama Desert, result from rain shadow effects, where mountains block moisture-laden winds. Coastal deserts, such as the Namib, occur due to cold ocean currents that reduce atmospheric moisture. Over time, these conditions create arid environments characterised by sparse vegetation and extreme temperatures.