In some regions the heat during the rainy season is worse than during the dry season because of the added discomfort of humidity. This is especially the case as you get closer to the coast. The weather is unpredictable of course, and rains do fail causing untold hardship to millions of subsistence farmers in Africa. Some years too much rain falls on the parched soil, and floods cause huge damage. In general, the "wet season" means buckets of rain fall from sky for a few hours a day, and then it will go back to being nice and sunny. If you're looking to save some money, traveling during the wet season is the way to go. It's also the best time to see birds and baby animals.
The Rainy (Wet) and Dry Seasons in West AfricaIt is generally hot year round in West Africa with average temperature hovering around 85 Fahrenheit (30 Celsius) during the day. The dry season in West Africa generally falls around the end of October - March. Closer to the coast it is always a little more humid even in the dry months, but there are less mosquitoes around and unpaved roads are passable. Given that most visitors come to West Africa to enjoy its beaches and cultures, the dry season is a good time visit. But it can get extremely hot, especially at the end of the dry season in March/April. The harmattan is also a factor during the dry season. It's a hot wind that carries Saharan sand, making it dusty and therefore not ideal for photographers looking for clear shots.
The rainy season in West Africa generally falls from the end of April - July on the coastal areas with a second shorter rainy season in September/October. The rains don't last all day and are much enjoyed when they fall. Water shortages are common in this region, so rain water is a blessing especially in cities on the coast. Further inland toward the desert, there's one rainy season and it tends to fall from July - September. This is the best time to go to countries like Mali, as temperatures cool down a little and rivers become more navigable.
The Rainy and Dry Season in East AfricaThe hottest time of year in East Africa is during the dry season from December to March. This is generally the best time to go trekking and enjoy a safari. Christmas can be baking especially at low elevations so keep that in mind and include a little beach time.
Northern Tanzania and Kenya experience two rainy seasons, the long rains from April to June and a shorter rain from November to December. The coastal areas can get very wet and humid during this time of year, so keep that in mind if you are planning to go to the beach. As you get further south in Tanzania, it's best to check out the southern African season below.
Ethiopia's seasons differ a little due to its mountainous nature, the wet season here falls from May - September and dry season from October - April.
The Rainy and Dry Season in Southern AfricaThe dry season in southern Africa is during the cooler months from May - August. This is the best time to go on safari. Nights can get quite chilly and close to freezing the further south you are and at higher elevations. So going on safari toward the end of the dry season, when it warms up a bit, is a good idea.
The rainy (wet) season is also the hottest time of year in southern Africa, and generally runs from November to March. The rains during this time of year will close down some of the more remote safari camps, this is especially the case in Zambia's Luangwa Valley. But visit the magnificentVictoria Falls during the wet season and you'll be soaked in awe.
Winter and Summer in North AfricaNorth Africa generally has mild winters (December - February), perfect for visiting tombs and monuments in hot deserts or taking a camel safari in the Sahara. Egypt's coast remains sunny and warm enough for swimming and diving. In Morocco the skies can get a little dull and rainy during the winter, it's too cold to enjoy the beaches.
The summer months in North Africa (June - September) are blazing hot. Head to the beaches or mountains if you plan to visit during this time, or make sure your hotel has a pool to cool off in the heat of the day. Summers are usually bone dry.
Winter and Summer in South AfricaSouth Africa is far south enough from the equator to enjoy a somewhat traditional summer and winter season (although its geography doesn't make this quite so simple). South Africa's summers (November to March) are generally warm with average temperatures around 77 Fahrenheit (25 C). Winters (June to August) can get quite cold especially at night with temperatures averaging around 50 Fahrenheit (10 C). In the Western Cape area most of the rainfall comes in the winters whereas in the north (Johannesburg and Kruger Park) and east (Durban) rainfall is heaviest in the summer months (causing some fantastic thunderstorms). Durban has an almost tropical climate and enjoys warm days even in winter.
If you are traveling to the Indian Ocean islands of Mauritius, Madagascar or Reunion, avoid the rainy season January - March because it is also "cyclone" season. Cyclones and hurricanes are extremely rare in The Seychelles.