In Aceh, the floods have affected five districts, injured hundreds of people, and prompted tens of thousands to flee their homes.
Syam Sumarno, a spokesman for Langkat regency, blamed heavy rains that began on Friday as well as the deforestation of the region for the devastation.
Lack of forest means the ground is less capable of retaining some of the water.
On December 26, 2004, Aceh was hit by the Indian Ocean tsunami, which left about 170,000 dead or missing in the province.
In Langkat, nearly 6,000 people are in temporary residences in shelters, while in Aceh the number is close to 50,000.
Eddy Syofyan, the North Sumatra information agency chief, was quoted by Antara state news agency as saying some roads connecting North Sumatra and Aceh had been cut by floods.
In Malaysia, across the strait of Malacca from Sumatra, the worst floods in 37 years have displaced nearly 100,000 people amid food shortages, looting and criticism of the government's handling of the crisis.