Drought is a prolonged period of abnormally low precipitation that leads to water shortages affecting agriculture, ecosystems, and human communities. It is a recurring natural hazard with significant economic impacts.
Drought is a complex, slow-onset natural hazard defined by an extended deficiency of precipitation relative to normal conditions that results in insufficient water to meet the demands of human activities and natural systems. Droughts are classified into four types: meteorological (precipitation deficit), agricultural (soil moisture deficit affecting crops), hydrological (reduced streamflow, reservoir levels, and groundwater), and socioeconomic (water supply failing to meet demand). The severity, duration, and spatial extent of droughts vary widely, from localized events lasting a few months to mega-droughts persisting for decades. Droughts can trigger cascading impacts including crop failures, livestock losses, wildfire, water rationing, land subsidence from groundwater over-pumping, ecosystem degradation, and human migration. The economic costs of drought in the United States average billions of dollars annually, making it the most costly natural hazard. Drought monitoring relies on indices such as the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Index (SPI), integrated through platforms like the U.S. Drought Monitor. Climate change is expected to intensify droughts in many regions through increased temperatures and altered precipitation patterns, though projections vary by location.