Brazil's national space agency, INPE, identified 6,803 fires in the Amazon region in July 2020, up from 5,318 the year before.
The figure is all the more troubling given that 2019 was already a devastating year for fires in the Amazon, triggering global outcry.
That has put pressure on Brazil, which holds around 60 percent of the Amazon, to do more to protect the massive forest, seen as vital to containing the impact of climate change.
The fires are largely set to clear land illegally for farming, ranching and mining.
Activists accuse Brazilian President Jair Bolsonaro, a far-right climate change skeptic, of encouraging the deforestation with calls to open up the rainforest to agriculture and industry.
On July 30 alone, satellites detected 1,007 fires in the Amazon, INPE said.
That was the worst single day for fires in the month of July since 2005, said environmental group Greenpeace.
"More than 1,000 fires in a single day is a 15-year record and shows the government's strategy of media-spectacle operations is not working on the ground," Greenpeace spokesman Romulo Batista said in a statement.
Bolsonaro has deployed the army to fight the fires, but activists say that does not go far enough to address the causes of the problem.
Fires increased 77 percent on indigenous lands and 50 percent on protected nature reserves from July 2019, Greenpeace said, showing how illegal activities are increasingly encroaching on those areas.
Fire season in the region typically runs from around June to October.
Exacerbating the situation this year, experts say the resulting smoke risks causing a spike in respiratory emergencies in a region already hit hard by COVID-19.
Brazil has more infections and deaths from the new coronavirus than any country except the United States: more than 2.6 million and 92,000, respectively.
INPE data had already showed it was a record-breaking July for fires in the Brazilian Pantanal, the largest tropical wetlands in the world.
There were 1,684 fires there last month, more than triple the number in July 2019.