Climate ranges from tropical rain forest in the Congo River basin to tropical wet-and-dry in the southern uplands to tropical highland in eastern areas above 2,000 meters in elevation. In general, temperatures and humidity are quite high. The highest and least variable temperatures are to be found in the equatorial forest, where daytime highs range between 30° C and 35° C, and nighttime lows rarely go below 20° C. The average annual temperature is about 25° C. In the southern uplands, particularly in southeastern Shaba, winters are cool and dry, whereas summers are warm and damp. The area embracing the chain of lakes from Lake Albert to Lake Tanganyika in the eastern highlands has a moist climate and a narrow but not excessively warm temperature range. The mountain sections are cooler, but humidity increases with altitude until the saturation point is reached a nearly constant falling mist prevails on some slopes, particularly in the Ruwenzori Mountains.

The seasonal pattern of rainfall is affected by Zaire's straddling of the equator. In the third of the country that lies north of the equator, the dry season (roughly early November to late March) corresponds to the rainy season in the southern twothirds . There is a great deal of variation, however, and a number of places on either side of the equator have two wet and two dry seasons. Rainfall averages range from about 1,000 millimeters to 2,200 millimeters. Annual rainfall is highest in the heart of the Congo River basin and in the highlands west of Bukavu and with some variation tends to diminish in direct relation to distance from these areas. The only areas marked by long four-month to five-month dry seasons and occasional droughts are parts of Shaba.

Data as of December 1993