Africa is a pear-shaped continent that stretches from the mid-latitudes of the Northern Hemisphere across the equator to the mid-latitudes of the Southern Hemisphere. Most would also find surprising that northern Africa is at a latitude equivalent to Norfolk, Virginia and that the southern tip is at a latitude equivalent to Buenos Aires, Argentina.

Africa is like a large, "Dagwood" climate sandwiched between a good deal of symmetry either side of the equator. The northern and southern tips have a Mediterranean climate with a cool, relatively wet winter and a sunny, warm and dry summer. This gives way quickly as you move equator-ward to hot, semi-arid or arid climates. Here you find the two of the world's most famous deserts, the Sahara and Namibia. Further equator-ward, the climates turn wetter with at least one wet season. Nearer the equator, we find a very wet tropical rain forest climate and in most places two wet seasons.

The primary cause of this mirror-image, climate layering is the seasonal movements of the Subtropical Highs of both hemispheres and the Intertropical Convergence Zones (ITCZ) that separate them.

In the winter seasons, extreme northern and southern areas of Africa find themselves poleward of the subtropical highs and vulnerable to passage of the polar front and polar cyclones. This can lead to periodic general rains and even high elevation snows along with chilly temperatures. Places where we find this happening include northern Morocco, Algiers, Tunisia, and northernmost Egypt in the Northern Hemisphere and the Cape region of South Africa in the Southern Hemisphere. During summer in these regions, the subtropical high dominates with warm and dry conditions. These conditions are typical of Mediterranean Climates.

MARRAKECH, MOROCCO

Within regions where the subtropical highs dominate, the accompanying sinking air leads to sunshine and hot, desert dry conditions. The countries here are parts of Morocco, Egypt, Libya, Algeria, and in the Southern Hemisphere, Namibia.

CAIRO, EGYPT

In regions where the ITCZ passes, we find a distinct rainfall maximum during its passage. This usually is at the time of the highest sun. In those areas where the ITCZ reaches just once a year, we find a single rainfall maximum. The fringe areas where the ITCZ barely reaches (the Sudan, the Sahel Belt countries of Mali, Upper Volta, Niger and Chad)) are the most vulnerable to drought and famine when the ITCZ is weak and out of position. Further equator-ward, the rainfall during the wet season is more dependable and heavier. Countries like Gambia, Sierra Leone, Senegal, Ghana and Guinea get relatively heavy rainfall during the Northern Hemisphere summer with disturbances that swirl along the tropical convergence zone. These tropical waves spin out into the Atlantic where they can become tropical storms or hurricanes.

FREETOWN, SIERRA LEONE

Closer to the equator, in places like southern Cameroon, Zaire, the Congo, Gabon, Liberia, the Ivory Coast, Rwanda, Kenya and Uganda, the ITCZ passes twice. As a result, these areas have a dual rainfall maximum.

Temperatures vary considerably across the continent, especially in winter. For example, in the north, in the winter, temperatures may drop below freezing and, in the extreme, even below zero. The continent's all-time record low was a surprising -11°F (February 11, 1935 at Ifrane at 5,364 feet elevation in Morocco). Closer to the equator, temperatures may reach 110°F in winter, which is the dry season. In between, in the desert, dry air means an abundance of sunshine and a large diurnal (day to night) temperature variation.

In summer, the Sahara experiences excessive heat. El Azizia in Libya reached 136°F on September 13, 1922. In areas and seasons where rainfall occurs, the temperatures are less extreme, but very high humidity makes the air extremely uncomfortable.

The Namibia desert in southwest Africa is much less hot than the Sahara in the north thanks to the cooling effect of the Benguela Current, which flows offshore.

Higher elevations also have cooler temperatures. Nairobi near the equator in the Kenya Highlands is a good example. Highest recorded temperature there has been just 87°F. Johannesburg over a mile high in the high veld in South Africa has a relatively pleasant and healthy climate. The area is subject to cold temperatures during winter nights due to the high elevation and relatively high latitude (26 degrees South) and dry air.

NAIROBI, KENYA

JOHANNESBURG, SOUTH AFRICA