Map from Google - Democratic_Republic_Congo

In the Democratic Republic of the Congo (formerly Zaire), a huge country in central Africa, the climate is equatorial, hot and humid all year round with no dry season, in the central area crossed by the equator where there is a vast rain forest (the second in the world after the Amazon), or tropical, hot all year round but with a dry season, usually of short duration, in both the areas north and south of the equator. The dry season occurs in opposite periods, from December to February (boreal winter) north of the equator, and from June to September (austral winter) south of the equator.
The rains occur in the form of downpour or thunderstorm (Congo is the country that receives the greatest number of lightning strikes in the world), usually in the afternoon, all year round in the equatorial zone, and in the long rainy season in the two tropical areas.
The country is largely occupied by the huge basin of the Congo River and its tributaries.
Most of the country is located at an altitude of a few hundred metres, between 300 to 800 metres (1,000 to 2,600 feet), which are often sufficient to mitigate the climate a bit; in some areas, such as the southeast, the altitude goes from 800 to 1,300 metres (2,600 to 4,300 ft), while in the easternmost part, near the Rift Valley lakes, there are also high mountain ranges.

Equatorial climate

Congo, Equatorial climate zone

In the equatorial zone, temperatures are stable throughout the year.
Here are the average temperatures of Kisangani, located near the equator, 400 metres (1,300 feet) above sea level.
Average temperatures - Kisangani
KisanganiJanFebMarAprMayJunJulAugSepOctNovDec
KisanganiJFMAMJJASOND
Min (°C)201920202019191919202020
Max (°C)313131313130292930303030
Min (°F)686668686866666666686868
Max (°F)888888888886848486868686

The rains in the equatorial zone are abundant, and hover around 1,700/2,000 millimetres (67/78 inches) per year. Rainfall experiences two maxima, at the two passages of the sun at its zenith (late March and late September), and given the inertia in the heating of the soil, the rainiest months are usually April-May and October-November. The least rainy periods are generally January-February and June-July, in which, however, usually more than 100 mm (4 in) of rain fall per month.
This is the average rainfall in Kisangani.
Average precipitation - Kisangani
KisanganiJanFebMarAprMayJunJulAugSepOctNovDecYear
KisanganiJFMAMJJASONDY
Prec. (mm)901151651801601151151551852302151651890
Prec.(in)3.54.56.57.16.34.54.56.17.39.18.56.574.4
Days9913151387914171512141

Tropical climate

Congo, areas with tropical climate

Both to the north and south of the equatorial zone (respectively, zone 1 and 2 in the map), the climate becomes tropical, because there is a clear dry season. The rainfall in the tropical climate zones averages normally between 1,000 and 1,700 mm (40 and 67 in) per year. Even the temperature varies to a greater extent, and is lower in the winter dry season, and higher in the summer rainy season, but especially in spring, at the end of the dry season.
Here are the average temperatures of Gemena, in the north-west (zone 1), at 400 metres (1,300 feet) above sea level.
Average temperatures - Gemena
GemenaJanFebMarAprMayJunJulAugSepOctNovDec
GemenaJFMAMJJASOND
Min (°C)192020212120202020201919
Max (°C)313332313130292930303031
Min (°F)666868707068686868686666
Max (°F)889190888886848486868688

In Gemena, 1,650 mm (65 in) of rain fall annually, with a maximum in the period from August to October. The dry season is short and lasts from December to February, a time when some showers are still possible.
Here is the average precipitation.
Average precipitation - Gemena
GemenaJanFebMarAprMayJunJulAugSepOctNovDecYear
GemenaJFMAMJJASONDY
Prec. (mm)3555125145165155180215195215120451650
Prec.(in)1.42.24.95.76.56.17.18.57.78.54.71.865
Days461112141212151617116136

In the tropical zone of the southern hemisphere (zone 2), both temperature and rainfall follow a reversed pattern.
The capital Kinshasa is located in the west, at about 300 metres (1,000 feet) above sea level, and at 4 degrees south latitude. Temperatures are high and fairly stable throughout the year, but in the austral winter (June to August) they become more pleasant.
Here are the average temperatures.
Average temperatures - Kinshasa
KinshasaJanFebMarAprMayJunJulAugSepOctNovDec
KinshasaJFMAMJJASOND
Min (°C)222222222219181921222222
Max (°C)303131313028272830303030
Min (°F)727272727266646670727272
Max (°F)868888888682818286868686

Rainfall in Kinshasa amounts to 1,400 millimetres (55 inches) per year. Within the rainy season from October to May, you can notice the two peaks, corresponding with the passages of the sun at its zenith (April and November).
Here is the average precipitation.
Average precipitation - Kinshasa
KinshasaJanFebMarAprMayJunJulAugSepOctNovDecYear
KinshasaJFMAMJJASONDY
Prec. (mm)155135170195125714351352551701387
Prec.(in)6.15.36.77.74.90.300.21.45.3106.754.6
Days10101315111014111614106

Tropical climate with long dry season

Congo, area having a tropical climate with a long dry season

In the short coastline overlooking the Atlantic Ocean, rainfall drops below 1,000 mm (40 in) per year, because in winter the cold Benguela current, which inhibits the formation of rain clouds, arrives here, but on the other hand it is able to bring a bit of cool air, and to create fog and low clouds.
Here are the average temperatures of Banana, on the coast.
Average temperatures - Banana
BananaJanFebMarAprMayJunJulAugSepOctNovDec
BananaJFMAMJJASOND
Min (°C)222222232220181921232323
Max (°C)303030302825252526272828
Min (°F)727272737268646670737373
Max (°F)868686868277777779818282

In this area, rainfall decreases to as low as 800 mm (31.5 in) per year; the rains are not particularly abundant, except maybe in April. In the austral winter, due to the cold sea current, it never rains.
Here is the average precipitation.
Average precipitation - Banana
BananaJanFebMarAprMayJunJulAugSepOctNovDecYear
BananaJFMAMJJASONDY
Prec. (mm)701251301706000052012080780
Prec.(in)2.84.95.16.72.40000.20.84.73.130.7
Days589125000157658

The sea temperature is high in the summer months, while it becomes a bit cool in winter, dropping to 22 °C (72 °F) in July and August. However, this coastal stretch, apart from the socio-political conditions of the country, does not lend itself to beach tourism, because of frequent cloud cover.
Here are the average sea temperatures.
Sea temperature - Banana
BananaJanFebMarAprMayJunJulAugSepOctNovDec
BananaJFMAMJJASOND
Sea (°C)272829282624222223252727
Sea (°F)818284827975727273778181

The country is more extended to the south than to the north (it stretches from the 13th parallel south to the 5th parallel north), and in addition in the south there are some areas located at higher elevations. The result is that in some areas the austral winter is more pronounced, dry and sunny, but very cool or even cold at night.
Here are the average temperatures of Lubumbashi, located in the far south, at 1,300 metres (4,250 feet) of altitude. Here in winter (June to mid-August), the temperature at night can drop to as low as 0 °C (32 °F). Additionally, you can notice the temperature increase in the second half of the dry season, between mid-August and October.
Here are the average temperatures.
Average temperatures - Lubumbashi
LubumbashiJanFebMarAprMayJunJulAugSepOctNovDec
LubumbashiJFMAMJJASOND
Min (°C)161616141088913151616
Max (°C)262626272625252730312826
Min (°F)616161575046464855596161
Max (°F)797979817977778186888279

In Lubumbashi, the winter dry season is very evident (it practically never rains from May to September) and long (lasting more than six months). Precipitation amounts to 1,200 mm (47 in) per year, with a maximum in summer (December to February), when the rains are abundant, and exceed 250 mm (10 in) per month.
Here is the average precipitation.
Average precipitation - Lubumbashi
LubumbashiJanFebMarAprMayJunJulAugSepOctNovDecYear
LubumbashiJFMAMJJASONDY
Prec. (mm)2552552606050005351652551240
Prec.(in)101010.22.40.20000.21.46.51048.8
Days24222092000151724124

Mountains

Congo, areas with a mountain climate

In the eastern part of the Democratic Republic of the Congo, there are mountain ranges, related to the East African Rift. In the Rift we find also a number of lakes, such as Lake Albert, located at 615 metres (2,000 feet) above sea level; Lake Edward, at 915 metres (3,000 ft); Lake Kivu, at 1,465 metres (4,805 ft); Lake Tanganyika, at 770 metres (2,500 ft); and Lake Mweru, at 920 metres (3,020 ft).
The mountains have an influence on precipitation, in fact the western side is more rainy, while the eastern side is sheltered from humid currents, so that in the central and southern part of Lake Tanganyika the rainfall drops below 1,000 mm (40 in) per year.
Here are the average temperatures of Goma, located at 1,500 metres (5,000 feet) above sea level, on the shores of Lake Kivu. Although we are at the equator, at this altitude, daytime temperatures are pleasant all year round, and cool at night.
Average temperatures - Goma
GomaJanFebMarAprMayJunJulAugSepOctNovDec
GomaJFMAMJJASOND
Min (°C)141414141413131313131313
Max (°C)252525252525252525252524
Min (°F)575757575755555555555555
Max (°F)777777777777777777777775

The rainfall amounts to 1,250 millimetres (50 inches) per year; from June to August the rains are fairly rare and not abundant.
Here is the average precipitation.
Average precipitation - Goma
GomaJanFebMarAprMayJunJulAugSepOctNovDecYear
GomaJFMAMJJASONDY
Prec. (mm)115951101401354530651151501451201265
Prec.(in)4.53.74.35.55.31.81.22.64.55.95.74.749.8
Days171720221775814202320190

The most imposing mountains of the country are the Ruwenzori mountains, which are located in the far east, on the border with Uganda, almost at the equator. The highest mountain is Mount Stanley, in Margherita Peak, 5,109 metres (16,762 ft), where there is also a glacier. These mountains are very wet, since they receive constant rainfall and are often covered with clouds; they are home to a variety of environments, which change with altitude: between 2,000 and 3,000 metres (6,600 and 9,800 ft) there is a montane forest; above 3,000 metres (9,800 ft) there are species able to withstand the night frost as well as the strong solar radiation during the day, and above 4,000 metres (13,000 ft) we find a moorland similar to the Alpine one. The Ruwenzori Mountains in the Congolese side are protected in the Virunga National Park (World Heritage Site by UNESCO), which extends to the south, beyond Lake Edward, to the other imposing mountain range, still on the border with Uganda, precisely the Virunga Mountains.
West of Lake Kivu we find the Mitumba Mountains, whose highest peaks are Mount Kahuzi, 3,308 metres (10,853 feet), and Mount Biega, 2,790 metres (9,154 feet), both protected in the Kahuzi-Biega National Park, UNESCO World Heritage Site, however, declared at risk because of illegal hunting and poaching.
Further south of the Virunga Mountains there are the Itombwe Mountains, which culminate in Mount Mohi, 3,475 metres (11,401 ft) high.

Giant Lobelia, Ruwenzori Mountains

The amount of sunshine in much of the Democratic Republic of Congo is never very good, because the strong solar radiation often causes cloudiness during the day, most likely from around noon and in the afternoon. On the other hand, in the early morning mists often occur, due to moisture evaporating from the ground, while on the coast, fog and low clouds often form, due to the cool sea current. The situation is different in the southernmost part (see Lubumbashi), where the dry season is more pronounced, and during the austral winter (May to September) the sky is often clear.
However, the sun at the equator is very strong, and requires adequate protection even when the sky is cloudy, especially at high altitudes.

When to go

There is no single best time to visit the Democratic Republic of the Congo, as the dry season comes at different times: in the tropical region north of the equator it runs from December to February; in the tropical region south of the equator (see Kinshasa) it goes from June to August; in the southernmost area (see Lubumbashi), there is little rain even in May, September and October, although in the latter two months it can get hot during the day, especially below one thousand metres (3,300 feet), see for instance the Kundelungu National Park.
In the equatorial zone, where it rains throughout the year, there is usually a drop in rainfall in two periods, January-February and June-July.

What to pack

In the equatorial zone, all year round, light clothing, of natural fibres, a light sweatshirt for the evening, umbrella or light raincoat for the rain showers.
In the tropical areas, in the rainy season, umbrella or light raincoat for the rain showers; in the relatively cool dry season (December to February in the north, June to September in Kinshasa and the south) you can add a sweatshirt and a light jacket, especially in the south and on the coast.
At low-mountain elevations, above a thousand metres (3,300 feet, see Lake Kivu and Goma, Lubumbashi), you can bring a sweatshirt and a light jacket for the evening, all year round.
In the far south, above a thousand metres (3,300 feet, see Lubumbashi), from May to August you can add sweater, warm jacket and hat for nights and early mornings.
For the top of the highest mountains, such as the Ruwenzori, all year round, winter clothes, jacket, hat, gloves.