Zanzibar's driest, sunniest window is June through October, coinciding neatly with mainland Tanzania and Kenya's dry safari season — which is exactly why the beach-finale combination is so popular and so easy to plan around one continuous dry spell. A second, quieter dry window runs late December through February. Avoid mid-March through May, when Zanzibar's long rains bring genuinely heavy, sustained downpours that can disrupt an entire beach stay. The Seychelles runs on a gentler, more forgiving calendar — it sits close enough to the equator that there is no true rainy season to avoid, just two shifts in trade winds. May through September brings the cooler, drier southeast trades (best for underwater visibility and calmer seas on the eastern islands); October through April brings warmer, more humid northwest winds with a slightly higher chance of afternoon showers, but also calmer conditions on the western beaches. Practically: if you are combining a safari with a beach finale, let the safari season drive your dates and treat the Seychelles as flexible almost any time of year — it is one of the only islands in the region with no genuine bad season.