World’s Driest Countries: Just 6 mm of Rainfall a Year
Not every country receives enough rainfall to support life. In some parts of the world, rain is so scarce that total annual precipitation amounts to only tens of millimetres.
Data from Our World in Data (OWID) show that Egypt recorded annual rainfall of just 6 millimetres (mm) in 2025, the lowest among the countries on this list.
For context, 1 mm of rainfall is equivalent to 1 litre of water collected over a flat area of 1 square metre. This means 6 mm of rainfall amounts to just 6 litres of water per square metre over the course of a year.
Egypt’s rainfall fell from 11 mm in 1940 to 6 mm in 2025. This is linked to its location in North Africa, where the Sahara Desert dominates and the climate is extremely arid.
Most of Egypt receives very little rain, while much of the country’s life and economic activity is concentrated along the Nile River and the northern coast. The Nile is an important water source amid the scarcity of local rainfall.
However, rainfall trends in dry countries have not moved uniformly. Qatar recorded an increase from 24 mm in 1940 to 59 mm in 2025. Bahrain’s rainfall also rose, from 22 mm to 43 mm, while Niger’s increased from 29 mm to 71 mm.
By contrast, Oman’s rainfall fell from 39 mm to 27 mm, while Saudi Arabia’s declined from 57 mm to 51 mm. These changes show that rainfall trends differ between countries, but a comparison of just two points in time is not enough to establish long-term climate change.
Annual rainfall can fluctuate because of geographical conditions and variations in atmospheric patterns—the systems of air movement, temperature distribution and pressure variations that shape weather and climate on Earth.
In subtropical regions, high-pressure systems can force air downwards, inhibit the formation of rain clouds and sustain dry conditions. The prevalence of deserts in North Africa and the Arabian Peninsula further reinforces this climate pattern.
Even so, conditions are not identical throughout each country. Saudi Arabia, for example, has a south-western region that receives more rainfall than most of the country. This shows how national averages can conceal substantial climatic differences within a single country.
For comparison, Indonesia’s annual rainfall increased from 2,193 mm in 1940 to 3,662 mm in 2025, according to OWID data. This is far higher than the figures for the countries on the list, consistent with Indonesia’s tropical climate and the supply of water vapour from the surrounding seas.