best time to visit zanzibar & pemba

January sits in the Kaskazi northeast monsoon, a hot dry spell with calm seas and clear water, but high humidity. Rainfall is low after the December showers ease, and the sea stays warm at around 29 degrees with visibility that often passes 30 metres.

Diving and snorkelling are genuinely good this month, and the whale shark season off nearby Mafia continues. The trade-off is heat and humidity: daytime air sits in the high twenties to low thirties with little of the cooling breeze the Kusi brings later in the year. Those who tolerate the heat will find quiet, clear conditions.

February brings some of the clearest water of the year under calm Kaskazi seas. It is one of the driest and hottest months, with visibility regularly above 30 metres and warm water around 29 degrees.

This is a strong month for diving and snorkelling on both Zanzibar and Pemba, where the deep wall sites reward the flat conditions. Whale sharks are still being seen off Mafia and manta rays are about. Heat and humidity are the cost: it is the hottest part of the year, so anyone sensitive to that should weigh it against the cooler months from June.

Early March can hold the calm, clear water of February, but the long rains usually arrive by mid-month. The winds drop before the rain comes, which often gives very flat seas and peak visibility in the first half.

From the middle of the month the masika builds: humidity climbs, showers become unpredictable and the sea grows less settled. The first ten days or so can be excellent for diving in the north, but conditions deteriorate as the month goes on, so timing matters and the back half is best avoided.

April is the wettest month of the year, the heart of the masika long rains. Heavy, prolonged downpours are common, run-off cuts underwater visibility sharply and seas turn rougher.

Many dive centres scale back or close and a number of beach lodges shut for the season. The landscape is green and the islands are quiet, but for a beach and diving trip this is the month to avoid. We would steer almost any client away from April.

May remains within the long rains, the second wettest month, easing only late on. Rainfall stays high, humidity is heavy and the sea can remain choppy with variable visibility.

Diving is unreliable and many camps and dive operations are still closed or running reduced. Conditions begin to settle towards the very end of the month as the Kusi sets in, but for most of May the beach and diving offer is poor. Better to wait for June.

June opens the cool dry season as the Kusi southeast monsoon sets in, the start of the prime beach months. Rainfall drops sharply from May, humidity falls and daytime air settles around a comfortable 28 to 29 degrees.

Seas calm and visibility is good. The Kusi makes the south and east coasts breezy, which suits kitesurfing, while the north and west stay sheltered for diving and swimming. Humpback whales begin their migration through these waters from now into September. After the long rains, this is the month conditions reliably turn.

July sits firmly in the cool dry season, one of the best all-round beach months. Rainfall is low at a handful of days, humidity is comfortable and the Kusi keeps the air fresh.

Water is cooler at around 25 degrees but visibility is excellent and most dive sites stay accessible. Pemba's wall dives and drop-offs are at their best in these settled months. Humpback whale sightings continue. The surface can be a little choppy on exposed coasts under the trade wind, but the sheltered sides remain calm.

August is the coolest of the dry months, with low rainfall and dependable diving. Daytime air sits near 28 to 29 degrees, nights are pleasant and humidity stays low under the Kusi.

Water is around 25 degrees with strong visibility, and Pemba in particular is noted for peak clarity in August and September. Humpback whales are still moving through, and green turtle hatching can be seen on Mafia's Juani Island. This is a comfortable, reliable month for both beach and dive trips.

September is widely rated among the very best months, with the Kusi easing and seas turning very calm. Rainfall is among the lowest of the year and visibility often exceeds 25 metres, with Pemba at its clearest.

As the wind drops, deeper and more exposed sites open up, which makes this a strong month for serious divers. Water begins to warm again towards 26 to 27 degrees and the last humpbacks pass through into early October. For the combination of calm water and clarity, it is hard to better.

October stays mostly dry and sunny with calm seas and superb visibility before the short rains approach. The Kusi has eased, water is warming towards 27 degrees and conditions for diving and snorkelling are excellent across Zanzibar, Pemba and Mafia.

The whale shark season off Mafia begins this month and runs through to March, which adds a real draw for clients willing to add the short hop south. Humidity starts to rise late in the month and the first vuli showers can arrive at the very end, but for most of October conditions are prime.

November brings the vuli short rains, much lighter and less disruptive than the masika. Expect brief afternoon showers between long spells of sun, with rising humidity and warm water near 29 degrees.

Diving stays very good: winds are light and seas often glassy before the Kaskazi picks up, and this is a peak month for whale sharks off Mafia. Fewer visitors and easier availability make it a quietly rewarding time for those who will plan around the odd shower rather than demand unbroken sun.

December sees the short rains taper off and the hot Kaskazi season return, with more rain than many expect early on. Zanzibar can see around 100 millimetres across the month, falling mostly in short bursts with plenty of good beach days between.

Seas are generally calm and warm and diving conditions are good, with whale sharks still off Mafia and manta rays about. It is a popular, festive and busy period over the holidays, so it trades the quiet of the shoulder months for reliable sun once the early showers clear.