Chapter II : Physical Geography
Part 4 : Climatology.

from : J. Roland and E. Duchesne, Cours Complet de Geographie : Le Congo Belge, Namur 1914, pp.14-15


Climatological Observations.

Entirely located in the tropical zone, the Congo has a constantly warm climate, and two seasons : a rainy and a dry season.
A. Seasons. - Because of the country's location on the equator, the two seasons present itself inversely throughout the year. In the north it is rainy season, if the dry season rules in the south, and vice versa. To the south of the equator, or more exactly to the south of the second parallel in the south, the rainy season lasts from October to May, the dry season from May to October. To the north of the equator, or more exactly north of the 5th parallel northern latitude, it is just inverted : the rainy season lasts from May to October, the dry season from October to May. In the equatorial band between the second southern and the fifth northern parallel, the seasons differ little; the entire year is rainy, and it is difficult to establish a dry season. But when one distances itself from the equator, one notes seasons a dry season or a less rainy season.
B. Precipitation - the amount of annual precipitation varies considerably from one region to the other; it increases from the coast toward the interior and also when one approaches the equator. It rarely reaches 2 m (2.055 at Eala, under the equator, in 1911); in the equatorial zone, the average annual precipitation is about 1,500 millimeters, well double the average annual rainfall of Belgium (720 millimeters). "It is an error to assume that during the rainy season it rains continuously. It is not so : there are two or three times per week, formidable thunderstorms called tornades, accompanied by diluvial showers, it is true; yet they do not last longer than two or three hours, after which the sky clears up again. The air is charged with electricity, especially in March and April, and almost every evening lightnings strike through the atmosphere into various directions. The tornades are sometimes accompanied by hail." (Goffart and Morissens)
C. Temperatures. - The rainy season is the warm season par excellance. The absolute maximum temperature observed in summer is just under 40 degrees centigrade (in March 1911, 38.7 degrees, at Eala). The thermometer marks, in the Congo, 30 and more degrees 150 times per year, in Belgium only 3 times on average. The average temperature per month does not sink below 26 degrees (in Belgium 9.5 degrees). But the annual variation is less than in Belgium : at the river delta, the difference between July, the least warm, and March, the warmest month, is not larger than 5.8 degrees; in Belgium it id 16.2 degrees between July and January. On the contrary, the daily balance, that is to say the deiiference between the temperature during the day and that at night, is bigger than in Belgium : 8.5 degrees at Banana, 13 degrees at Luluabourg, compared to 7.2 degrees at Uccle (Belgium). A fact of great importance from a hygienical point of view, making precautions against nightly temperatures indispensable. On the high plateaus of Katanga and the elevated regions toward Lake Kivu, the cold is sometimes so strong that the indigenous suffer and it produces a white jelly. The absolute minimum temperature observed until today in the colony is 0.5 degrees.
D. Winds. - Except in the eastern region, the dominant winds are those from the west and the southwest; in the east, notably in Katanga, the winds from the southeast rule.
E. Hygienic Conditions. - During the rainy season, the sultry heat and the air saturated with water cause pernicious fevers, across the coastal and central regions of lesser altitude; spread by mosquitos, malaria is endemic. There are three other widespread diseases : the tropical anaemia, hematury and dysentery.
Two diseases particularly strike the coloreds : Beri-Beri, a nervous affection which causes considerable weight loss and the paralyzation of the limbs, and the sleeping sickness, also called trypanosomiase. This latter, which also attacks the whites, is transmitted by stings of the tsetse fly and degenerates into an epidemic which causes great devastation.
The variole is the most frequent epidemic disease; it affects frequently the skin and sometimes turns ulcerous.

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Last revised on February 13th 2002

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