What counts as a drought?
Short answer
A drought is a shortage of precipitation over an extended period. It is a normal part of climate in many places and can last weeks or years. [S2]
Three ways to measure it
- Meteorological drought: how dry it is and for how long. [S2]
- Hydrologic drought: the effect on water supply, such as stream flow, reservoirs and groundwater. [S2]
- Agricultural drought: the effect on farming, such as soil moisture and irrigation water. [S2]
The U.S. National Integrated Drought Information System (NIDIS) runs drought research and early warning. [S1]
Claims
- id: C1 claim: Drought is a deficiency in precipitation over an extended period. source: S2 evidence: "Drought is a deficiency in precipitation over an extended period."
- id: C2 claim: Meteorological drought is based on dryness and length of the dry period. source: S2 evidence: "Meteorological drought is based on the degree of dryness (rainfall deficit)"
- id: C3 claim: Hydrologic drought looks at water supply impacts. source: S2 evidence: "Hydrologic drought is based on the impact of rainfall deficits on the water supply"
- id: C4 claim: NIDIS supports drought research. source: S1 evidence: "NIDIS supports drought research through advancing the scientific understanding"
Sources
- [S1] What is Drought?. NOAA. https://www.drought.gov/what-is-drought . License: US government work, public domain. Accessed 2026-11-04.
- [S2] Understand Drought and Know How to Respond. NOAA. https://www.weather.gov/safety/drought . License: US government work, public domain. Accessed 2026-11-04.
License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).
License: CC-BY-4.0 · Summary by iinventedlight (AI-assisted). Sources: NOAA, What is Drought?, US government work, public domain; NOAA, Understand Drought and Know How to Respond, US government work, public domain.
Cite this
iinventedlight. 2026. "What counts as a drought?" iinventedlight Library, iil:note:c6gxngb6, version of 2026-11-04. https://iinventedlight.com/library/notes/drought-basics/. License: CC-BY-4.0.
@misc{iil_note_c6gxngb6,
author = {{iinventedlight}},
title = {{What counts as a drought?}},
howpublished = {iinventedlight Library},
year = {2026},
date = {2026-11-04},
url = {https://iinventedlight.com/library/notes/drought-basics/},
note = {Permanent ID iil:note:c6gxngb6. License: CC-BY-4.0.},
}Spotted a mistake? Use the MCP feedback tool or email hello@iinventedlight.com.
For language models and agents: start at /llms.txt. This page in Markdown: /library/notes/drought-basics.md.