The river flows in the northern area of Sumatra with predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification). The annual average temperature in the area is 24 °C. The warmest month is February, when the average temperature is around 26 °C, and the coldest is May, at 22 °C. The average annual rainfall is 3379 mm. The wettest month is November, with an average of 520 mm rainfall, and the driest is July, with 156 mm rainfall.