Why do deserts have such low humidity?

Deserts have low humidity because they receive minimal rainfall and experience high evaporation rates. Dry air descending in subtropical high-pressure zones inhibits cloud formation, reducing precipitation. Coastal deserts, like the Atacama, are influenced by cold ocean currents that cool the air, preventing moisture from rising. The lack of vegetation further contributes to low humidity, as there is minimal transpiration to release water vapour into the atmosphere.