Most of Namibia is classified as an arid to semi-arid region (the line being crossed from semi-arid to arid when evaporation exceeds rainfall). Most of it has a sub-tropical 'desert' climate, characterised by a wide range in temperature (from day to night and from summer to winter), and by low rainfall and humidity. The northern strip follows the same pattern, but has a more moderate, less dry climate. Note that although the terms 'summer' (November to April) and 'winter' (May to October) are sometimes used, they are not as applicable as, say, in a European maritime climate.
Temperatures range widely from very hot to very cold, depending on the height of the land above sea level and the month. From April to September, in the 'dry season', it is generally cool, pleasant, clear and dry. Temperatures average around 25ºC during the day, but nights are much colder. Frost is possible in the higher areas and the deserts. October and November are still within the 'dry season' but then the temperatures are higher, especially in the lower-lying and more northerly areas.
Most of Namibia's rain falls in the summer, from around December to March, and it can be heavy and prolonged in the northern regions of Owamboland and Caprivi. The further south or west you go, the drier it becomes, with many southern regions of the Kalahari and the whole of the coastal Namib Desert receiving no rainfall at all some years. In this 'rainy season' temperatures occasionally reach 40ºC, and sometimes you may find it humid in the north.
The beginning of the year, in January
, is midsummer. Then it's hot and fairly damp with average maximum temperatures around 25–35°C and average minima around 10–20°C (depending exactly where you are). These averages, however, hide peaks of well over 45°C in the desert.
On a typical day during the rains, the sky will start blue and by early afternoon the clouds will appear. In the late afternoon there will be an hour's torrential rain on some days. Such tropical storms are spectacular; everything feels terrifically fresh afterwards. However, you wouldn't want to be caught outside. By the early evening the sky will usually begin to clear again.
The frequency of the rains decreases, and they cease around March
. From then the heat is waning and the land gradually cools and dries out. The nights quickly become cooler, accentuating the temperature difference between the bright, hot days and the clear nights. May
is a lovely month: there is minimal chance of rain, nights are not yet too cold, and many of the summer's plants are still lush and green.
the nights are cold, approaching freezing in desert areas where night game drives can be bitter. July
are winter, when the average maximum temperatures are around 15–25°C and the average minima are around 0–10°C. That said, you'll still find yourself wearing shorts and a T-shirt during the day, and getting sunburnt if you are not careful. Clouds will be a rare sight for the next few months.September
is another super month, dry and clear, yet not too hot. By then most green vegetation is fading as the heat begins to build. Everything is dry. All through October
the heat mounts, and by November
it is very hot during the day. However, the humidity is still exceedingly low, so even the high temperatures feel quite pleasant.
By November the air seems pregnant with anticipation. Everything is dry, awaiting the rains. Though the clouds often build up in the afternoon, they won't usually deliver until at least December
. When (and if ) the rains do arrive, they are a huge relief, dropping the temperatures at a stroke, clearing the air and reviving the vegetation.
The coastal strip
Temperatures on the Namibian coast follow a similar overall pattern, though it may seem very different from one day to the next. Here the climate is largely determined by the interaction between warm dry winds from inland and the cold Benguela Current. The sea is too cold for much evaporation to take place and, consequently, rain-bearing clouds don't form over the coast. Most of the coast is classified as desert – rainfall is an extremely low 15mm per annum on average, and in some years there may be none.
However, hot air from the interior mixes regularly with cold sea air to produce a moist fog that penetrates up to 60km inland. This happens regardless of season, and has done for millennia. It is this periodic morning fog which provides the desert's only dependable source of moisture, and the Namib's endemic flora and fauna have evolved to take advantage of it.