[1][2][3] The river flows along the northwest area of Sumatra, which has a predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification).

[4] The annual average temperature in the area is 25 °C.

The warmest month is March, when the average temperature is around 26 °C, and the coldest is January, at 23 °C.

[5] The average annual rainfall is 3953 mm.

The wettest month is November, with an average of 588 mm rainfall, and the driest is June, with 175 mm rainfall.