Rwanda has two dry seasons and two wet seasons, and the distinction matters — particularly for gorilla trekking, where muddy slopes can make the hike significantly harder.
Long dry season: June to September. This is peak season. The weather is clear, the trails are at their best, and gorilla tracking is easiest. Expect higher prices and demand for permits. Book gorilla permits three to six months ahead.
Short dry season: December to February. Nearly as good as the long dry season, with slightly fewer visitors. A good option if the June–September window doesn't work.
Long wet season: March to May. Heavy, persistent rain for weeks at a time. Trails are slippery and muddy. Some roads become difficult. Gorilla trekking is still possible, and the forest is strikingly lush. Permit prices don't drop (Rwanda has fixed pricing), but you'll have the national parks largely to yourself.
Short wet season: October to November. Shorter rains, generally manageable. The landscape is green and photogenic. A reasonable compromise if you can't travel in peak months.
The highlands, including the Volcanoes area, are cooler year-round — bring a fleece regardless of season. Kigali, at about 1,500m, stays warm but rarely hot.