The river flows in the central area of Sumatra which has a predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).[3] The annual average temperature in the area is 23 °C. The warmest month is August, when the average temperature is around 24 °C, and the coldest is January, at 22 °C.[4] The average annual rainfall is 2899 mm. The wettest month is November, with an average of 403 mm rainfall, and the driest is June, with 115 mm of rain.[5]
