Namibia's weather patterns
Namibia is among the most arid countries on Earth. The weather is characterised by high daytime temperatures, short seasonal summer rainfalls, high rates of evaporation and crystal-clear blue winter skies. It is wettest in the northeast, where total annual rainfalls can reach 650 millimetres or more, but half of the country receives less than 350 millimetres of rainfall in a year. Farther south and west, rainfall declines and becomes increasingly erratic; it is rare along the entire coast. Yet potentially unbearable weather along the country's western edge is ameliorated by cool sea breezes, and fog which enshrouds the coastal belt on about one in three days of the year providing an important water source for desert plants and animals.
These weather patterns experienced across Namibia are strongly influenced by a dominant high-pressure system over the ocean, and the cold Benguela ocean current. Although these and other factors determine our broad climate, the air and the oceans are part of one entire global system – a system that is always in dynamic balance. Changes in one part of the system affect the rest of it. Cyclical perturbations in atmospheric pressure in the eastern and western tropics of the Pacific Ocean influence ocean surface temperatures causing what is known as the El Niño Southern Oscillation when warm water builds up in the equatorial region of South America. The influence of this event is felt on weather patterns throughout the world. For Namibia specifically, El Niño tends to increase the probability that the country will experience drier conditions for a time. La Niña is the opposite side of this cycle; it occurs when Pacific Ocean surface waters are cooler than normal and increases the likelihood of wetter conditions in Namibia.
Seasons in Namibia are not equally divided across the year. Spring and autumn are short transitional periods between the summer months (October– March) and the mid-year winter months. Although summer is considered the rainy season, for much of the country rainfall is low, variable and unpredictable.