A crisis cabinet has been set up by the São Paulo state government to deal with wildfires which have put 30 Brazilian cities on alert.
Flames have killed two people and smoke has disrupted traffic on a dozen highways, while the capital, São Paulo, is shrouded in a grey haze.
Soaring temperatures and low humidity are stoking dangerous fire conditions in the state, which has endured a prolonged drought.
Local government said two employees at an industrial plant in the city of Urupes had died on Friday while fighting a fire, without providing more details, Reuters reported.
Brazil has recently experienced a huge wildfire in the Pantanal wetlands and vast flooding in the state of Rio Grande do Sul.
The state government has also warned forest fires could spread rapidly from gusts of wind, potentially razing large areas of natural vegetation.
Writing on social media, Governor Tarcísio de Freitas said: “We currently have 30 cities on high alert for large fires and we are working to control the situation and ensure safety.”
In a separate post he later wrote: “São Paulo is facing a difficult time and we are committed, joining forces, to control the fires and keep people safe.
“We were in the field throughout the day to ensure a prompt response to the most affected areas, such as Piracicaba, Barrinha, Sertãozinho and Ribeirão Preto. We will not rest until the situation is back to normal.”
Meanwhile, the state’s capital São Paulo has been covered by a dense grey fog.
“With gusts of wind, the fire can spread rapidly,” the government warned in a statement.
“Fires emit dense and toxic smoke that harms the environment and human health, causing problems to the respiratory system and cardiovascular disorders,” it added.
The situation was critical in São Jose do Rio Preto, a city of 480,000 inhabitants, where more than 335 fires have been registered in recent days, prompting school closures, AFP reported.
Brazil has been hit by a series of extreme weather events, most recently a massive wildfire in the Pantanal wetlands in June.
At the time climate experts said this year’s wildfire season had started earlier and is more intense than in previous years.
Earlier this year in May, Brazil also experienced once-in-a-century flooding in the state of Rio Grande do Sul which left more than 170 people dead and displaced more than half a million people from their homes.