The town of Sao Paulo went dark for an hour Monday as winds mixed with a cold front blew smoke from Amazonas and Rondonia, located more than 1,600 miles away, the BBC reported.
One person living in Sao Paulo told the BBC, "It was as if the day had turned into night. Everyone here commented because even on rainy days, it doesn't usually get that dark. It was very impressive."
This year, there have been a record number of fires in the rainforest, according to Reuters.
So far in 2019, there have been 72,843 fires detected, 83% more than the same timeframe last year and the most since record-keeping started in 2013, Reuters reported.
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In the past week, there have been almost 10,000 new forest fires in Brazil, burning areas that would otherwise be fighting against global warming.
Many of the fires are man-made, with farmers setting them deliberately to clear land for cattle ranches, according to Reuters.
Experts said the surge in illegal fires started after President Jair Bolsonaro took office, the BBC reported.
Bolsonaro countered critics, saying the data "doesn't relate to the reality," according to the BBC.
Despite Bolsonaro's stance, the state of Amazonas has declared a national emergency, the BBC reported.