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Ethiopia Climate
Diverse rainfall and temperature patterns are largely the
result of Ethiopia's location in Africa's tropical zone and
the country's varied topography. Altitude-induced climatic
conditions form the basis for three environmental zones--
cool, temperate, and hot--which have been known to
Ethiopians since antiquity as the dega, the weina dega, and
the kolla, respectively.
The cool zone consists of the central parts of the western
and eastern sections of the northwestern plateau and a small
area around Harer. The terrain in these areas is generally
above 2,400 meters in elevation; average daily highs range
from near freezing to 16°C, with March, April, and May the
warmest months. Throughout the year, the midday warmth
diminishes quickly by afternoon, and nights are usually
cold. During most months, light frost often forms at night
and snow occurs at the highest elevations.
Lower areas of the plateau, between 1,500 and 2,400 meters
in elevation, constitute the temperate zone. Daily highs
there range from 16°C to 30°C.
The hot zone consists of areas where the elevation is lower
than 1,500 meters. This area encompasses the Denakil
Depression, the Eritrean lowlands, the eastern Ogaden, the
deep tropical valleys of the Blue Nile and Tekezé rivers,
and the peripheral areas along the Sudanese and Kenyan
borders. Daytime conditions are torrid, and daily
temperatures vary more widely here than in the other two
regions. Although the hot zone's average annual daytime
temperature is about 27°C, midyear readings in the arid and
semiarid areas along the Red Sea coast often soar to 50°C
and to more than 40°C in the arid Ogaden. Humidity is
usually high in the tropical valleys and along the seacoast.
Variations in precipitation throughout the country are the
result of differences in elevation and seasonal changes in
the atmospheric pressure systems that control the prevailing
winds. Because of these factors, several regions receive
rainfall throughout most of the year, but in other areas
precipitation is seasonal. In the more arid lowlands,
rainfall is always meager.
In January the high pressure system that produces monsoons
in Asia crosses the Red Sea. Although these northeast trade
winds bring rain to the coastal plains and the eastern
escarpment in Eritrea, they are essentially cool and dry and
provide little moisture to the country's interior. Their
effect on the coastal region, however, is to create a
Mediterranean-like climate. Winds that originate over the
Atlantic Ocean and blow across Equatorial Africa have a
marked seasonal effect on much of Ethiopia. The resulting
weather pattern provides the highlands with most of its
rainfall during a period that generally lasts from mid-June
to mid-September.
The main rainy season is usually preceded in April and May
by converging northeast and southeast winds that produce a
brief period of light rains, known as balg. These rains are
followed by a short period of hot dry weather, and toward
the middle of June violent thunderstorms occur almost daily.
In the southwest, precipitation is more evenly distributed
and also more abundant. The relative humidity and rainfall
decrease generally from south to north and also in the
eastern lowlands. Annual precipitation is heaviest in the
southwest, scant in the Great Rift Valley and the Ogaden,
and negligible in the Denakil Depression.
Data as of 1991
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