Droughts can occur anywhere on the planet, but they are most prevalent and long-lasting in arid climates. Areas of the globe that experience high humidity and precipitation can have droughts when rainfall totals taper off over a long period of time, but these droughts are usually temporary in nature.
The term "drought" is relative, since different regions receive vastly different amounts of rainfall. For example, the city of Atlanta, Georgia receives around 50 inches of rain per year, and if that total fell by half, it would represent a severe drought. But if the city of Albuquerque, New Mexico received 25 inches of rain in a year, it would represent almost triple the normal amount of precipitation.
Droughts tend to be more severe in arid climates because these biomes typically experience very little rainfall and have poor aquifer support for plants and wildlife. It would take many years if not decades of reduced rainfall to drain the Amazon rainforest of moisture, while a single dry season in the western United States may send water stocks to dangerous levels. Human development can exacerbate droughts, especially when landscapers attempt to bring in plants ill-suited to a dry climate, or when construction damages or destroys erosion-resistant plants that help hang on to moisture to supply the region.