By the HMNDP Editorial Team | Independent reporting on lawn care, landscaping, water, and the green industry.
Last reviewed: June 2026
What causes droughts, in one paragraph
Droughts are caused by a lasting shortage of precipitation, usually driven by persistent high-pressure systems that push sinking air over a region and block rain clouds from forming. When this pattern holds for weeks, months, or years, water supplies fall below normal. Natural climate cycles like El Nino and La Nina, jet stream shifts, human water overuse, and a warming atmosphere that pulls more moisture out of soil all deepen the deficit.
A drought is not simply a hot day or a dry week. The U.S. Geological Survey (USGS) and NOAA define drought as a period of drier-than-normal conditions long enough to cause water shortages. The key words are “drier than normal” and “extended.” A rainforest and a desert can both enter drought; what matters is the shortfall relative to what that place usually gets.
The 5 main causes of drought
The five main causes of drought are: (1) below-average precipitation, (2) persistent high-pressure systems that block rain, (3) ocean-atmosphere cycles like El Nino and La Nina, (4) higher temperatures that speed evaporation, and (5) human water demand and land-use change. Most real droughts combine several of these at once rather than a single trigger.
- Deficient precipitation. The root cause. Less rain and snow than the long-term average, sustained over time. Every other cause either produces this deficit or makes its effects worse.
- Persistent high-pressure systems. A dome of high pressure forces air to sink. Sinking air warms and dries, which suppresses cloud formation and steers storm tracks around the region.
- El Nino and La Nina. Shifts in Pacific Ocean temperatures reorganize global rainfall, drying some regions for months at a time.
- Elevated temperatures. Heat increases evaporation from soil, reservoirs, and plants, draining water even when rainfall is only slightly below normal.
- Human demand and land use. Overuse of rivers and aquifers, plus deforestation and paving, reduce the water available and change how landscapes hold moisture.
10 causes of drought (the full list)
Here are 10 causes of drought, spanning natural and human factors. The first several are natural climate mechanisms; the last several are human-amplified drivers. Real droughts usually stack two or more of these on top of a baseline precipitation deficit, which is why they are hard to predict and slow to break.
- Below-average rainfall and snowfall over an extended period.
- Blocking high-pressure ridges that force air to sink and dry out.
- El Nino (warm Pacific phase) shifting rain away from certain regions.
- La Nina (cool Pacific phase) drying the southern United States and other zones.
- Jet stream shifts that steer storm systems around a region.
- Subtropical high-pressure belts (the Hadley cell) that keep deserts dry.
- Monsoon failure, when seasonal rains arrive late, weak, or not at all.
- Rising temperatures and evaporation, largely tied to climate change.
- Groundwater and surface water overuse by cities, farms, and industry.
- Deforestation and land-use change that reduce local moisture recycling.
How droughts form and develop over time
Droughts form slowly. They begin when a weather pattern, often a stubborn high-pressure system, blocks rain for weeks. As the deficit grows, soil dries, then streams and reservoirs drop, and finally water supplies for people and farms run short. Scientists call drought a “creeping” hazard because there is no single moment it starts. It builds and compounds.
The sequence matters because it explains the different drought types. A short hot spell hits crops first. A multi-year rain shortage empties reservoirs and aquifers. The same starting cause can grow into different problems depending on how long it lasts.
- Weeks 1 to 4: A high-pressure system stalls. Rainfall drops below normal. This is the start of meteorological drought.
- Weeks 4 to 12: Topsoil dries out. Crops and lawns show stress. This is agricultural drought.
- Months 3 to 12+: Streamflow falls and reservoirs and groundwater decline. This is hydrological drought.
- Ongoing: Water demand exceeds supply, triggering restrictions and shortages. This is socioeconomic drought.
This is why a drought can “start” one month and not become a crisis until the next year. If you manage a lawn or landscape, the early agricultural-drought phase is where you feel it first. Our guide on how to prepare for a drought covers what to do once soil moisture starts dropping.
Atmospheric conditions that block rain
The most direct cause of drought is a high-pressure system that parks over a region and forces air downward. Sinking air warms as it descends, which lowers its humidity and prevents clouds from forming. Rain needs rising, cooling air; high pressure delivers the opposite. When one of these “ridges” persists, it deflects storms for weeks.
Two atmospheric features drive most drought:
- Blocking highs. A stationary high-pressure dome. The 2012 to 2016 California drought featured a persistent ridge nicknamed the “Ridiculously Resilient Ridge” that pushed Pacific storms north into Canada.
- The subtropical high-pressure belt. Near 30 degrees latitude, the descending arm of the Hadley cell keeps air dry year-round. This belt is why the Sahara, the Australian Outback, and the U.S. Southwest are naturally arid and drought-prone.
Natural drivers vs human-amplified drivers
Drought causes fall into two groups that the top search results rarely separate cleanly: natural climate drivers that have always existed, and human-amplified drivers that make droughts hotter, longer, and more damaging. Natural drivers set the pattern; human drivers raise the stakes. The table below splits them so you can see which is which.
| Natural drivers | What it does | Human-amplified drivers | What it does |
|---|---|---|---|
| El Nino / La Nina | Shift global rainfall for 6 to 18 months | Warming-driven evaporation | Dries soil faster at any rainfall level |
| Jet stream shifts | Steer storms around a region | Groundwater depletion | Removes stored buffer against dry years |
| High-pressure ridges | Block cloud formation for weeks | Deforestation | Cuts local moisture recycling |
| Subtropical high belt | Keeps deserts permanently dry | Land-use change / paving | Reduces infiltration and soil moisture |
| Monsoon variability | Delays or weakens seasonal rains | Over-allocation of rivers | Leaves no reserve when flow drops |
The key insight: climate change does not usually cause the rain deficit itself. It intensifies the drought by raising temperatures. NASA and NOAA research shows that hotter air pulls moisture from soil and vegetation faster, turning a moderate rainfall shortfall into a severe drought. This is called “aridification,” and it is why modern droughts run hotter than those of a century ago.
How El Nino and La Nina cause droughts
El Nino and La Nina are opposite phases of a Pacific Ocean cycle called the El Nino-Southern Oscillation (ENSO). They change where warm water sits in the Pacific, which shifts where storms form. This reorganizes rainfall across continents, drying some regions for many months while flooding others. NOAA tracks ENSO because it is one of the strongest predictors of seasonal drought.
- El Nino (warmer central and eastern Pacific) often brings drought to Australia, Indonesia, southern Africa, and parts of India, while wetting the southern United States.
- La Nina (cooler eastern Pacific) tends to dry the southern United States, including Texas and the Southwest, and can weaken parts of the North American monsoon.
Because these cycles last 6 to 18 months, they are a leading cause of multi-season droughts. The severe 2011 Texas drought lined up with a strong La Nina. Forecasters watch Pacific sea-surface temperatures months ahead precisely because they signal which regions face a dry season.
The four types of drought and their distinct causes
There are four types of drought, and each has a different cause and timeline. Meteorological drought comes from a rainfall deficit. Agricultural drought comes from dry soil hitting crops. Hydrological drought comes from a prolonged shortfall draining rivers and aquifers. Socioeconomic drought comes from demand outrunning supply. Most competitors define these types but never trace why different causes produce different types.
| Type | Primary cause | Typical timeline | What it hits first |
|---|---|---|---|
| Meteorological | Precipitation below normal for the region | Weeks to months | Nothing yet; it is the rainfall metric |
| Agricultural | Low soil moisture, often plus heat and evaporation | Weeks to a season | Crops, lawns, gardens, rangeland |
| Hydrological | Extended deficit draining rivers, lakes, aquifers | Months to years | Reservoirs, streamflow, groundwater |
| Socioeconomic | Water demand exceeding available supply | Any duration | People: restrictions, prices, shortages |
Here is the causal logic the SERP is missing. A single hot, dry summer produces agricultural drought fast because shallow soil moisture disappears within weeks. But it may never reach hydrological drought if reservoirs stayed full going in. A hydrological drought needs a longer deficit, often multiple dry seasons, to draw down deep storage. The cause is the same category (too little water), but duration and depth of the deficit decide which type you get.
Socioeconomic drought is the one humans control most directly. A region with modest rainfall can avoid it with careful water management, while a wetter region can trigger it through overuse. Understanding your local soil and water needs, including practical measures like mulch depth and coverage, helps. Our references on how many cubic feet are in a yard of mulch and how much a yard of mulch weighs help homeowners plan water-retaining ground cover before a dry spell arrives.
Why some regions have droughts more than others
Some regions face droughts more often because of their fixed position in the global circulation. Areas near 30 degrees latitude sit under the subtropical high-pressure belt, where sinking air keeps rainfall low. Regions that depend on a single rainy season, like monsoon Asia, are exposed whenever that season fails. Distance from oceans and mountain rain shadows also raise drought risk.
- Subtropical zones (Southwest U.S., North Africa, Australia, the Middle East) sit under permanent descending air.
- Monsoon-dependent regions (India, the Sahel, Southeast Asia) get most of their rain in one window; a weak monsoon means a dry year.
- Rain-shadow regions lie downwind of mountains that strip moisture from incoming air before it arrives.
- Continental interiors far from oceans receive less moisture-laden air to begin with.
Human demand then concentrates the risk. Fast-growing cities and irrigation-heavy farming in already dry regions, such as the U.S. Southwest drawing on the Colorado River, mean even a normal dry cycle can push the area into shortage.
Impacts of drought that link back to the cause
Drought impacts trace straight back to the water deficit that caused them. Crops fail when soil moisture runs out. Water supplies shrink as reservoirs and aquifers drop. Ecosystems suffer as streams shrink, wildfire risk climbs, and habitats dry. The severity of each impact depends on how long and how deep the underlying precipitation shortfall ran.
- Agriculture: Reduced yields, crop loss, and livestock stress. Agricultural drought is often the first economic hit.
- Water supply: Falling reservoirs and groundwater force restrictions, higher costs, and in severe cases hauling or rationing.
- Ecosystems: Lower streamflow harms fish, dries wetlands, and raises wildfire risk as vegetation cures.
- Land: Dry, bare soil erodes and can trigger dust events, as in the 1930s Dust Bowl, which combined severe drought with poor land management.
Who defines and tracks drought
Drought in the United States is defined and monitored by federal science agencies. NOAA and its National Centers for Environmental Information (NESDIS/NCEI) run climate monitoring. The USGS tracks streamflow and groundwater. NASA provides satellite soil-moisture data. Together they feed the U.S. Drought Monitor, the weekly map that classifies drought severity from D0 (abnormally dry) to D4 (exceptional).
These agencies matter for accuracy because “drought” is always relative to a place’s normal. Their long-term precipitation and streamflow records set the baseline that defines when conditions are drier than normal. For landscape-scale effects and how dry conditions reshape planted ground, see our companion explainer on what causes drought in a landscape.
Frequently Asked Questions
What are the 5 main causes of drought?
The five main causes of drought are below-average precipitation, persistent high-pressure systems that block rain, ocean-atmosphere cycles like El Nino and La Nina, higher temperatures that speed evaporation, and human water demand combined with land-use change. The precipitation deficit is the root cause; the others either create that deficit or worsen its effects. Most real droughts combine several of these factors at once.
What are 10 causes of drought?
Ten causes of drought are: low rainfall and snowfall, blocking high-pressure ridges, El Nino, La Nina, jet stream shifts, the subtropical high-pressure belt, monsoon failure, rising temperatures and evaporation, groundwater and surface water overuse, and deforestation or land-use change. The first several are natural climate mechanisms; the last several are human-amplified. Actual droughts usually stack two or more on top of a precipitation deficit.
How do droughts form and develop over time?
Droughts form when a weather pattern, often a stalled high-pressure system, blocks rain for weeks. As the deficit grows, topsoil dries first, then streams and reservoirs drop, and finally water supplies for people run short. Scientists call drought a “creeping” hazard because it builds gradually with no single start point. A drought can begin one month and not become a crisis until the next year.
What is the difference between meteorological, agricultural, and hydrological drought?
Meteorological drought is a precipitation deficit compared with a region’s normal, lasting weeks to months. Agricultural drought is low soil moisture that stresses crops and lawns, often within weeks, especially with heat. Hydrological drought is a longer shortfall that drains rivers, reservoirs, and groundwater over months to years. The same starting deficit becomes different types depending on how long and how deeply it persists.
Do humans and climate change cause droughts?
Humans and climate change usually amplify droughts rather than start them. NASA and NOAA research shows warming raises temperatures, which speeds evaporation and dries soil faster, turning a moderate rainfall shortfall into a severe drought. Groundwater overuse, deforestation, and paving reduce stored and recycled water. Natural climate patterns typically trigger the rain deficit; human drivers make droughts hotter, longer, and more damaging.
How do El Nino and La Nina cause droughts?
El Nino and La Nina are opposite phases of a Pacific Ocean cycle that changes where warm water sits and where storms form. This reorganizes rainfall across continents. El Nino often dries Australia, Indonesia, and southern Africa, while La Nina dries the southern United States, including Texas and the Southwest. Because each phase lasts 6 to 18 months, they commonly cause multi-season droughts.
How long does it take for a drought to happen?
A drought can take anywhere from a few weeks to several years to develop. Agricultural drought can appear within three to four weeks when hot, dry weather drains topsoil. Hydrological drought, which lowers reservoirs and groundwater, usually needs months or multiple dry seasons. Because drought builds gradually, there is no single moment it begins, which is why forecasters watch conditions continuously.
What role do high-pressure systems and the jet stream play in droughts?
High-pressure systems force air to sink, which warms and dries it and prevents clouds and rain from forming. When a high-pressure ridge stalls over a region for weeks, it deflects storms and starves the area of moisture. The jet stream steers those storm tracks; when it shifts north or buckles, it routes rain-bearing systems around a region, deepening and prolonging drought.
Why do some regions have droughts more than others?
Some regions have droughts more often because of their fixed place in global circulation. Areas near 30 degrees latitude sit under the subtropical high-pressure belt, where sinking air suppresses rain. Monsoon-dependent regions rely on one rainy season and suffer when it fails. Rain shadows behind mountains and dry continental interiors add risk, and heavy human water use in these zones concentrates it further.