An equatorial, humid and hot climate
Zanzibar, Pemba and Mafia have an equatorial climate, due to their latitude of 6° below the equator and their oceanic location. This means mild to warm weather all year round, ideal for lazing around. Temperatures fluctuate between 22 and 26°C on average, verging on 30°C in the hottest months (especially February). Rainfall during the African monsoon season is concentrated between the beginning of March and the end of May (very heavy and continuous), and the short rainy season occurs from the end of September to the end of November (fairly irregular and discontinuous). The archipelago's rainfall is highly variable: around 300 mm per month in the main rainy season, much less in the short wet season - 170 mm per month - compared with 30 mm per month in the dry season. In other words, the sun shines almost eternally, especially from early June to late September, which corresponds to winter (June is the coldest month). But the climate remains equatorial and humid, particularly during the short, more variable dry season from early December to late February. It can be sweltering hot in February (equatorial summer), so it can rain a few drops in the evening when the air is really saturated with heat. At any time of day, the sky offers cloudy landscapes of a beauty that would have delighted the Impressionist painters.
An archipelago that can be enjoyed almost all year round
The ideal time to visit the Zanzibar archipelago (including Unguja, Pemba and Mafia) is during the long dry season from early June to late September, although August is the coldest month of the year. The short dry season from December to February is also ideal, although February is very, very hot. To a lesser extent, you can enjoy the archipelago's beaches in October and November, as the short rainy season is still pleasant. The African monsoon season is to be avoided altogether, as it's a continuous curtain of rain that falls from the sky, and in any case hotels are closed and roads impassable.
The monsoon winds make the rain and the sun shine
"It's the monsoon": this phrase is typical of Asian countries, especially India, where the monsoon winds - of which there are several currents - bring heavy rains. But on the Indian Ocean, these same winds also bring water-laden clouds. This is the "African monsoon", typical of this part of the continent.
The word "monsoon" comes from the Arabic mawsim, meaning season, because when it blew, the weather was favorable for navigation in the Indian Ocean, towards India. These winds played a decisive role in the island's history: it was thanks to them that dhows from Asia (and India in particular) landed in Zanzibar. The thousand-year-old dhows that exist on both shores of the Indian Ocean are called "dhows" in Zanzibar. Thanks to this wind, the island was part of the famous incense route between Egypt, Yemen and India in ancient times.
From a meteorological point of view, this seasonal phenomenon combines a set of winds that blow over vast intertropical regions. The monsoon phenomenon is caused by a temperature differential: here, the land heats up and cools down faster than the sea, which remains at a constant temperature. These winds blow northeast over the Zanzibar archipelago during the six months of the year that make up the summer (December to May), bringing powerful and abundant rain during the last three months. They then change direction abruptly, blowing in the opposite south-westerly direction during the six months of winter (June to November), bringing rain towards the end of the cycle, but less heavily than in summer. These abrupt changes result in very marked climatic cycles between the dry and wet seasons.
The wind, kitesurfing's ally
The Zanzibar archipelago has two windy seasons: winter, from mid-June to October, when the south-west monsoon wind blows, and summer, from mid-December to mid-March, when the north-east monsoon wind blows. Unguja is the only island in the archipelago to offer kitesurfing on its entire eastern side, and its main spot is to the southeast, at Pajé and Jambiani. This is the place to go for experienced riders. It's Zanzibar's Mecca for kiteboarders! You can ride the Zanzibar reef where the coral reef stops before the deep blue ocean, and the waves rise up to 3 meters high. The wind is constant, neither too strong nor too weak, and the lagoon is very flat, making it an incredible kitesurfing spot. The ideal season for kitesurfing is from mid-June to mid-September, then from mid-December to the end of February. Beginners have more choice: if they want to try the sport, they can find a few schools in other villages further north on the east coast (Kiwemgwa, Matemwe and Nungwi). You start out with waist-high water, which is handy for getting back on the kite without fighting against currents and waves, while falling safely into the water. The lagoon is the ideal place to start gliding.
Warm and clear waters, ideal for diving
Due to its constant equatorial climate and Indian Ocean setting, the water around the Zanzibar archipelago also has a fairly constant temperature, hovering around 27°C. Underwater visibility varies from 20 to 40 meters, depending on the spot, depth and wind strength, but is spectacular, particularly around Mnemba atoll. The best period for maximum visibility and the best chance of encountering large marine mammals is from September to March, except in December when winds can be quite strong and disturb the water. Turtles and dolphins can be seen all year round, but whale sharks migrate to Mafia's warm waters only from early October to late February. In July and August, visibility is less good due to a fairly strong, constant wind that clouds the water; it's also the coolest month, and some warm-water-loving migratory animals are not present.
