The mechanism is brutally simple. El Niño disrupts rainfall, the forest dries out, and fires that people light for land management — clearing pasture or crop fields — escape and burn freely through the parched understory. Lightning ignites less than 1 percent of fires in the Brazilian Amazon, so nearly every fire burning now was started by humans, Morton said.

The drought itself is extreme. Brazil's National Institute of Meteorology reported that Manaus rainfall was 95 percent below normal in August 2026 and 60 percent below normal in September.

What comes next, and when?

Morton's team lays out a timeline:

• Fires around Santarém and Manaus should keep burning until the rainy season arrives in December 2026 or January 2027.
• The next wave is expected in November and December in the Brazilian states of Roraima, northern Pará, and Amapá, plus parts of Venezuela, Guyana, and Suriname.
• Drought and fire risk peak last in the southern Amazon, around August and September 2027, in Brazil and Paraguay.

"It's so striking — and frustrating — that this is happening all over again," Morton said. Many of the same forests that burned during the El Niño events of 2023 and 2015 are burning again. That matters ecologically: most rainforest species aren't adapted to fire, and Morton warns that earlier fires partially charred trees, degrading the forest and leaving what remained more likely to burn — likely more intensely this time.

"Given the intensity of this El Niño, this really is the year for people to avoid burning at all costs," Morton said.

Are the satellites missing fires?

Here's the part that should temper any clean official numbers. Shane Coffield, an assistant research scientist at the University of Maryland based at NASA Goddard, estimates 50 to 70 uncontrolled fires are burning in the Santarém region alone.

His analysis suggests the standard satellite products undercount the problem. "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, referring to NASA's Fire Information for Resource Management System.

The culprit is physics, not sloppiness. Dense smoke, clouds, and tree canopy block satellite sensors from detecting a fire's infrared signal — especially low-intensity fires creeping along the forest floor. "On some of the smokiest days, we have very few detections from MODIS and VIIRS, and we know that isn't right," Coffield said.

His VIIRS-based work, part of a NASA Earth Action project, aims to flag these "candidate fires" and share their locations with MapBiomas, a network of universities, NGOs, and tech companies that maps fires and land-use change in the Amazon.

What does this change for people on the ground?

For the regions north and south of the current burn zone, there is still time to prepare — which, in practice, means not lighting management fires at all this year. For Manaus and Santarém, the honest answer is: hold on until the rains. And when officials or datasets quote fire counts, treat them as a floor, not a ceiling.