Nyungwe has two dry seasons — June to September is the longest and the most reliable for trail conditions and primate tracking. A short dry season runs from late December to early February. The rest of the year is wet, sometimes very wet, and trails turn into slippery clay slides under the canopy.
Birding is best in the wet seasons, when more species are breeding and the resident populations are joined by migrants. Temperatures stay cool year-round at the park's altitude — usually 15 to 20°C during the day, dropping into single digits at night. Bring warm layers regardless of season.