In one afternoon the city saw more rain than the historical average for the entire month of February, according to Rio Civil Defense, and the municipality declared a state of public disaster in Petropolis.
Videos posted on social media show pictures of cars pulled by strong currents, and records show that there were 207 calls to the fire department related to torrential rain.
Claudio Castro, governor of the state of Rio de Janeiro, traveled to Petropolis and announced that firefighters and public officials from other cities would help deal with the effects of the torrential rains.
A merchant who was cleaning up his damaged shop told Reuters he was surprised by the flooding.
“It arrived by surprise, and gradually started pouring in… It was very difficult,” said merchant Henrique Pereira.
“We’ve lost everything,” another trader, Regian Dias, told the news agency.
Brazilian President Jair Bolsonaro, who is currently on a trip to Russia, tweeted that he had spoken to ministers and asked for “immediate help” to be sent to the victims.
At the beginning of February, at least 24 people died after heavy rains in Sao Paulo, causing floods and landslides across the Brazilian state.
More than 1,546 families have been displaced, according to a statement issued by the government civil defense, which also said that among the dead were at least eight children.
At the end of December, it was announced that the death toll from the floods and torrential rains that had swept the Brazilian state of Bahia since November had risen to 20.
State officials say the floods also caused two dams to explode, leaving an estimated 62,800 people homeless.