NASA Tracks El Niño's Fire Cascade as Smoke Smothers Manaus

NASA's Earth Observatory reported on 15 October 2026 that fire activity has climbed sharply across the central and eastern Amazon since September, with smoke from fires on both banks of the Amazon River pushing air quality in Manaus to among the worst levels on a regional index. The agency published the account alongside an image captured by the MODIS instrument on NASA's Aqua satellite on 12 October 2026.

According to NASA Earth Observatory, the zone of elevated fire activity stretches from forests around the commercial and transport hubs of Manaus and Santarém to the mouth of the Amazon River. The increases have been visible in NASA's Fire Information for Resource Management System (FIRMS), the Global Fire Emissions Database (GFED) and NASA Worldview.

Smoke over a city of two million

On 12 October, heavy smoke settled over Manaus, capital of the Brazilian state of Amazonas. City officials reported fine particulate matter (PM2.5) values above 135 micrograms per cubic meter, which NASA described as the second-worst rating on a regional air quality index. The agency said the smoke disrupted daily life in a city of more than two million people, with schools closed and citywide events and children's sports leagues cancelled as officials warned of hazardous air, citing news reports.

The drought underlying the burning has been severe. NASA cited Brazil's National Institute of Meteorology as reporting that rainfall in Manaus was 95 percent below normal in August 2026 and 60 percent below normal in September.

The second domino

Douglas Morton, an Earth system scientist at NASA's Goddard Space Flight Center, described the burning around Santarém and Manaus as part of a "cascade" of fire across the tropics that accompanies the shifted rainfall patterns of an El Niño. The sequence begins with drought and peat fires in Indonesia along the equator, then moves to this part of the Amazon. Morton and colleagues from the University of California, Irvine; Vrije Universiteit Amsterdam; and the University of Maryland described the pattern in a 2017 study published after the fire season that accompanied the 2015–2016 El Niño, and NASA said they observed it again in 2023.

NASA reported that drought, fire and smoke have affected parts of Indonesia since August, with hundreds of homes razed in October and thick smoke covering whole islands on most days. "Now, in the Amazon, we're seeing the second domino in the cascade fall," Morton said, pointing to the increase in fires in Pará and Amazonas.

Morton and colleagues expect the next wave farther north in November and December, in the Brazilian states of Roraima, northern Pará and Amapá and in parts of Venezuela, Guyana and Suriname. Drought and fire risk are then expected to peak around August and September 2027 in the southern Amazon regions of Brazil and Paraguay.

"It's so striking—and frustrating—that this is happening all over again," Morton said, noting that many forests that burned during the 2015 and 2023 El Niño events are burning again. He added that some fires are likely to burn more intensely this time because earlier fires partially charred trees and left the remaining forest more vulnerable. Most rainforest species are not adapted to fire, NASA noted.

Morton expects the fires near Santarém and Manaus to continue until the rainy season arrives in December 2026 or January 2027. For regions farther north and south, he said there is still time to prepare: "Given the intensity of this El Niño, this really is the year for people to avoid burning at all costs."

Counting the fires satellites miss

Morton said that because the Brazilian Amazon is normally so wet, lightning ignites less than 1 percent of fires there, meaning most of the current fires were started by people. Many began as management fires — clearing shrubs from pastures or crop residue from fields — and escaped into the parched forest understory.

Satellite analysis indicates 50 to 70 uncontrolled fires are burning in the Santarém region alone, according to Shane Coffield, a University of Maryland assistant research scientist based at NASA Goddard. As part of a NASA Earth Action project, Coffield is examining VIIRS observations to find fires that fall below the threshold for inclusion in FIRMS products, and plans to share these "candidate fires" with MapBiomas, a network of universities, NGOs and technology companies that maps fire and land-use change in the Amazon.

"For the area around Santarém, we've identified about 40 percent more fires than you'll see in active fire counts from FIRMS," Coffield said. He attributed the gap to dense smoke, clouds and canopy cover blocking the infrared signal, particularly from lower-intensity understory fires: "On some of the smokiest days, we have very few detections from MODIS and VIIRS, and we know that isn't right."

The full item is available from NASA Earth Observatory.