The wet months
Mahale Mountains in the Green Season
From November the rain returns to the lakeshore and the mountain disappears into cloud by mid-morning. This page sets out what that actually costs you in chimpanzee trekking, when the camps shut entirely, and who still has good reason to come.
If you only want the answer
The green season splits into two halves. November, December, January and February stay open, with harder, longer treks and a real chance of migratory birds and low rates. Then every camp closes from 1 March to 31 May and the park is effectively off the map. Come in the open half if you value solitude, birding and a green mountain over a short trek. Wait for June to October if a fast, low trek to the M group is the point of your trip.
What rain does to a chimpanzee trek
Every other safari season changes what you see. At Mahale it changes what you have to do to see it. The M group's whereabouts each day depend on where roughly sixty to seventy-five chimpanzees found fruit that morning, and in the wet months that fruit is everywhere, including far up the mountainside. Trackers still find them on almost every outing, but the walk in gets longer, steeper and muddier as the season builds.
Think in hours rather than minutes. A trek that a dry-season visitor finishes before the day heats up can turn into a real climb through slick forest trails once the rains have the mountain in full fruit. Pack proper grip, a rain layer, and the patience for a full morning rather than a stroll up from the beach.
The window that is actually open
Treat the green season as two separate seasons, because the camps do. November through February stays open end to end, priced as low season at most properties and, at Greystoke, priced at its very lowest in February. Then, without exception, the shore shuts down: Greystoke and Mbali Mbali Mahale both close from 1 March, and neither reopens before 1 June. Nkungwe Beach Lodge's own dry-season window effectively skips the same three months.
TANAPA's bandas and campsites at Kasiha remain bookable year-round in principle, but this is where the closure bites hardest for anyone determined to travel anyway. Scheduled flights pause completely through March, April and May, so a visitor still moving has to arrange an independent boat, usually from Kigoma, into a park with no functioning tourism infrastructure. Do not plan a trip for those three months. Plan around them instead.
The lake does not close with the camps
Lake Tanganyika answers to the wind more than the rain, and the wind gets less predictable as the season builds. Boat transfers between the airstrip and camp still run through November, December, January and February, but afternoons bring squalls that can push a crossing earlier or later than planned, so build slack into your first and last day.
Swimming stays on the table regardless of the month, since the water off Mahale's beaches carries no bilharzia risk in any season. What you lose is the glass-clear visibility of September and October. Snorkelling over the cichlid beds still works through the open green-season months, just with more sediment in the water after a storm.
The forest makes its own case
Rain built this forest, and the wet months are when it shows. Waterfalls that thin to a trickle by September run hard again, the gallery forest along the trek routes carries a fuller list of butterflies, and Mount Nkungwe's slopes turn a green that photographs like nowhere else on this lake. Ranger-led hikes to the falls continue outside the full closure, short trips at $20, longer ones at $25.
This is also when the migratory birds are in the forest, present from November through April and overlapping almost exactly with the open half of the green season. If your interest runs past the chimpanzees to the rest of the recorded checklist, this is your window, not the dry months.
Who should come, who should wait
Come in the open green season if you are a birder chasing the November to April migrants, a photographer who wants a green mountain and storm light rather than dust, or a returning visitor who has already had the easy dry-season trek and wants the harder, wilder version. February in particular rewards anyone chasing value, since Greystoke's rates bottom out then, right before the camp closes for the year.
Wait for July through October if you want the trek itself to be short and close to certain. That is when the M group feeds low near the shore and a walk can be over before the morning heat builds, and it is the only stretch where a first-time visitor with limited days should plan a trip at all. Anyone on a tight schedule, travelling with young children, or unwilling to risk a long uphill walk belongs in the dry months, not these.