The Selous Game Reserve is situated in the very south of Tanzania. Huge and watered by Rufiji River, it has two distinct ecological zones: grasslands that dominate north of the river and - to the south and constituting 80% of the park - miombo woodland. Ranging from semi-arid to humid, the park experiences a single rainy season, from mid-November through to April, with yearly average levels of precipitation 750mm to 1,300mm. East is drier, hotter and temperatures range between 17.9°C and 37.3°C. The park becomes steadily wetter the further west one goes, and temperatures drop slightly (14°C-36°C).
On paper, the rainy season in Selous spans 6 months, but it is a slow starter, builds gradually and only really gets going late December. In a normal year, June and November are the buffer months - June being dry but relatively green, December seeing the beginning of real rain. In terms of viewing wildlife, peak season is July through November, when it is very dry, the cover next to useless and when the animals mass along the river and remaining water sources. Bird watching is best between December and April.