The river flows in the southeast area of Sumatra with predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).[7] The annual average temperature in the area is 25 °C. The warmest month is September, when the average temperature is around 28 °C, and the coldest is January, at 22 °C.[8] The average annual rainfall is 3248 mm. The wettest month is December, with an average of 547 mm rainfall, and the driest is September, with 40 mm rainfall.[9]