English: As autumn’s rains began to dampen Eastern Russia, the summer wildfire season continued to ravage Siberian forests in early September 2023.

On September 7, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired a true-color image that captures features of the transition from summer to autumn in Eastern Russia. At that time, rain-driven sediment poured from the Amur River into the Strait of Tartary while a long dense plume of smoke drifted over the Sea of Okhotsk and southward over the northern tip of Sakhalin Island.

The Strait of Tartary is sandwiched between mainland Russia and Sakhalin Island, and it connects the Sea of Japan with the Sea of Okhotsk. The northern part of the strait, also known as the Amur Liman, receives freshwater from the Amur River. The Amur is the world’s tenth-longest river, which flows east along the Chinese-Russian border before turning northeast and emptying into the strait.

Flooding is common along the river from spring through autumn. In the spring, melting snow and thawing soils lead to a surge of meltwater, or freshet. The surge of water carries sediments and organic materials into the strait, coloring its waters brown. A second pulse of water in late summer and autumn comes from rainfall that accompanies the monsoon and sweeps more materials into the river and eventually into the strait.

The smoke drifting over the scene most likely originates, at least in part, in a group of fires burning in Khabarovsk Region almost 950 kilometers (590 miles) to the northwest. According to Global Forest Watch, fire season in the Khabarovsk Region typically begins in late May and lasts about 14 weeks—roughly the last week of August. With a hot, dry summer following a warm winter, this year’s fire season across Siberia has been particularly intense. Fires were reported by late April and fires continue to burn across Siberia, including the Khabarovsk Region, despite dropping temperatures, cloudy days, and rain.