The river flows in the northern area of Sumatra with predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).[2] The annual average temperature in the area is 25 °C. The warmest month is August, when the average temperature is around 26 °C, and the coldest is December, at 22 °C.[3] The average annual rainfall is 2568 mm. The wettest month is December, with an average of 572 mm rainfall, and the driest is March, with 114 mm rainfall.[4]
