The river flows in the northern area of Sumatra with 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 June, when the average temperature is around 27 °C, and the coldest is October, at 22 °C.[4] The average annual rainfall is 3483 mm. The wettest month is December, with an average of 522 mm rainfall, and the driest is March, with 178 mm rainfall.[5]
