The world's most drought-prone regions are the African Sahel and Horn of Africa, the Middle East and Central Asia, the American West and Great Plains, southeastern Australia, northeastern Brazil, and the Mediterranean rim. All of them sit near subtropical high-pressure belts, deep inside continents, or in the rain shadow of mountains — and all are becoming drier as warming raises evaporation.
What Counts as a Drought — and Why It Matters
Drought is often called a "silent disaster." It has none of the visual drama of a hurricane or an earthquake, but its cumulative effects on food production, water supply, ecosystems, and public health make it the natural hazard that touches the most people worldwide. United Nations assessments estimate that drought has affected well over 1.5 billion people since 2000, with agricultural losses running into the hundreds of billions of dollars.
Part of what makes drought so difficult to manage is that it has no agreed starting gun. Unlike a flood, it develops over weeks or months, and specialists distinguish several overlapping kinds:
- Meteorological drought — rainfall persistently below the local normal. This is the first domino to fall.
- Agricultural drought — soil moisture insufficient for crops at the stage of growth when they need it. A well-timed dry spell can be harmless; a badly timed one is ruinous.
- Hydrological drought — depleted rivers, reservoirs, and groundwater. This lags the rainfall deficit, sometimes by a year or more.
- Socioeconomic drought — the point at which water shortage begins to disrupt supply of food, power, or drinking water to people.
A region can be in hydrological drought while rainfall has already recovered, which is why reservoir levels and public restrictions often lag the weather headlines.
The geography behind the pattern
Drought-prone regions are not scattered at random. Three geographic factors dominate. The first is the subtropical high-pressure belt around 20–35° north and south, where descending air suppresses cloud formation — the same mechanism that builds the Sahara and the Australian interior. The second is continentality: places far from any ocean, such as Central Asia, receive little moisture-bearing air. The third is the rain shadow, where mountains wring out moisture on their windward side and leave the lee dry, as the Andes do for Patagonia and the Sierra Nevada does for the Great Basin. Our guide to the desert biome covers those mechanisms in more depth.
The Sahel and Horn of Africa
The Sahel — the semi-arid transition zone stretching more than 5,000 km from Senegal to Sudan, between the Sahara and the tropical forests to the south — is among the most drought-vulnerable places on Earth. Its rain arrives in a single monsoon season of three to four months. A shortfall of just 10–20% in that season's total can be the difference between a harvest and a famine.
The Sahel droughts of the 1970s and 1980s are estimated to have killed on the order of 100,000 people and displaced millions, permanently reshaping the region's demography and politics. The shrinkage of Lake Chad — down roughly 90% from its 1960s extent — has compounded the pressure on the four countries that share it.
Further east, the Horn of Africa — Somalia, Ethiopia, and Kenya — runs on a cyclical rhythm driven by the Indian Ocean Dipole and by El Niño and La Niña. Between 2020 and 2023 the region endured five consecutive failed rainy seasons, its worst drought in four decades, leaving more than 20 million people facing acute food insecurity. Climate projections for the region point to further drying.
Central Asia and the Middle East
This belt contains the highest concentration of water-stressed countries anywhere. Two episodes illustrate what chronic scarcity does.
The Aral Sea, once the world's fourth-largest lake, has shrunk to roughly a tenth of its original volume since the 1960s after Soviet-era irrigation schemes diverted its feeder rivers, the Amu Darya and Syr Darya, to grow cotton. The exposed lakebed is now a source of salt-and-pesticide dust storms that carry serious health consequences across the surrounding region. It is the most-cited example anywhere of a water body destroyed by allocation decisions rather than by climate.
Syria's drought of 2006–2010 was the most severe in the country's instrumental record. Crop failure was widespread, and roughly 1.5 million farmers and herders moved to already-strained cities. Researchers are careful not to claim the drought caused the civil war that followed, but many identify it as a significant aggravating factor that amplified existing economic and political stress — the clearest case study of water scarcity acting as what security analysts call a "threat multiplier."
The American West and Great Plains
Tree-ring reconstructions indicate that the American West has been living through its driest multi-decade stretch in at least 1,200 years. Lake Mead and Lake Powell, the two largest reservoirs in the United States, have repeatedly fallen to record lows. The Colorado River that fills them supplies roughly 40 million people across seven states and northern Mexico, and is over-allocated by design: the 1922 compact that divided its water was negotiated during an unusually wet period and assumed a flow the river has rarely matched since. In most years the river no longer reaches the sea.
Beneath the Great Plains lies a second, slower crisis. The Ogallala Aquifer supports roughly 30% of all irrigated agriculture in the United States, but decades of pumping have drawn it down far faster than it recharges — in parts of western Kansas the water table has dropped by more than 60 metres. Some projections suggest sections could become effectively unusable within 25 to 50 years.
The precedent everyone invokes is the Dust Bowl of the 1930s, when drought combined with unsuitable ploughing practices displaced some 2.5 million people. On a single day — "Black Sunday", 14 April 1935 — an estimated 300 million tonnes of topsoil were stripped from the plains.
Southern Hemisphere and Mediterranean Hotspots
Three further regions belong on any serious list.
- Southeastern Australia. The Millennium Drought of roughly 2001–2009 pushed Australia's Murray-Darling Basin to the brink and triggered one of the largest water-reform programmes ever attempted. The 2017–2019 drought caused billions in agricultural losses despite rainfall only slightly below average — a textbook "hot drought" in which heat, not rainfall deficit, did the damage.
- Northeastern Brazil. The sertão has a centuries-long history of secas, with drought closely tracking Atlantic sea-surface temperature patterns. It remains one of the most drought-exposed densely populated regions on Earth.
- The Mediterranean rim. Spain, Portugal, Italy, Greece, and North Africa sit at the poleward edge of the subtropical high. Climate models are unusually consistent in projecting a drying Mediterranean, making it one of the clearest regional signals in the entire climate record.
Drought vs Desertification vs Aridity: A Comparison
These three terms are used interchangeably in casual writing, but they describe quite different things, and conflating them leads to bad reasoning about solutions.
- Aridity is a permanent climate condition. The Atacama is not in drought — it is simply arid, and always has been. Some Atacama weather stations have never recorded measurable rain. Aridity is the baseline, not a departure from it.
- Drought is a temporary departure from that baseline. A drought in Ireland and a drought in Sudan involve completely different absolute rainfall totals, because drought is defined relative to local normals. Crucially, drought is reversible: the rain returns.
- Desertification is land degradation in drylands. It is a change to the land itself — loss of topsoil, vegetation, and productive capacity — usually driven by human land use such as overgrazing or unsustainable irrigation, often triggered or accelerated by drought. Unlike drought, it does not simply reverse when the rain comes back.
The practical distinction matters enormously. You manage aridity with appropriate crops and infrastructure. You manage drought with storage, allocation rules, and insurance. You prevent desertification with land-use policy — and once it has happened, reversing it takes decades. Confusing the second for the third is why some emergency drought responses have made long-run degradation worse.
How Climate Change Is Changing the Picture
Warming intensifies drought through a mechanism that requires no change in rainfall at all. Higher temperatures increase evaporation from soils, lakes, and reservoirs while simultaneously increasing the water demand of crops and people. A region can therefore receive its normal rainfall and still slide into deficit — the "hot drought" phenomenon now visible from the American Southwest to southeastern Australia. Our overview of the geography of climate change covers the broader pattern.
Two further shifts are emerging. "Flash droughts" — rapid-onset events that develop in weeks rather than months, driven by heatwaves — are becoming more common and are far harder to prepare for. And the loss of mountain snowpack, which functions as natural seasonal storage for basins from California to Central Asia, removes a buffer that existing water infrastructure was built to assume.
Final Thoughts
Drought reaches more people than any other natural hazard, and the regions most exposed to it are defined by durable geography: subtropical subsidence, continental interiors, and rain shadows. What is changing is not the map so much as the intensity — rising temperatures are pushing already-marginal regions past thresholds their agriculture and infrastructure were designed around. The response levers are unglamorous but well understood: efficient irrigation, realistic allocation rules that reflect actual river flows rather than optimistic historical ones, groundwater metering, and land management that prevents temporary drought from hardening into permanent degradation.