The river flows in the central area of Sumatra with predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).[4] The annual average temperature in the area is 23 °C. The warmest month is March, when the average temperature is around 24 °C, and the coldest is January, at 22 °C.[5] The average annual rainfall is 3766 mm. The wettest month is November, with an average of 336 mm rainfall, and the driest is July, with 113 mm rainfall.[6]