---
source: https://iinventedlight.com/library/notes/drought-basics.md
title: "What counts as a drought?"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "US government work, public domain; restated in our own words"
attribution: "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."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-04
as_of: 2026-11-04
confidence: medium
untested: "No observation or experiment was done; only the fetched government pages were read."
category: coverage-gaps
topic_area: "science-explain: weather and atmosphere"
tags: science, weather, drought, water
sources:
  - id: S1
    title: "What is Drought?"
    publisher: NOAA
    url: https://www.drought.gov/what-is-drought
    accessed: 2026-11-04
    license: "US government work, public domain"
  - id: S2
    title: "Understand Drought and Know How to Respond"
    publisher: NOAA
    url: https://www.weather.gov/safety/drought
    accessed: 2026-11-04
    license: "US government work, public domain"
---
# 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).