Storms and floods battering the state, home to some 10.9 million people, have also left more than 337,000 displaced while another 146 people were still unaccounted for, civil defence said.
Heavy rains have caused several rivers and lakes in the region to hit their highest levels ever, while floods blocked streets and disrupted logistics, triggering a shortage of essential goods in certain areas.
Weather forecaster MetSul said that most Rio Grande do Sul cities should see rains on Friday, adding there is a "high risk of storms". They should persist until Monday, it added in a statement.
In Canoas, one of most affected cities near state capital Porto Alegre, over 6000 people were staying in a college gymnasium turned into shelter.
Aparecida de Fatima Fagundes said she had been struggling to sleep there as she could not stop thinking about "the worst day" of her life.
"I keep remembering people saying 'help', 'help'," she said.Â
"It was horrible."
State government said more than 385,000 people had no water services, while some 20 cities were out of telecom services.
On Thursday, the federal government announced a package of aid measures to help Rio Grande do Sul, which included bringing forward payment of social benefits and providing cheaper credit to farmers and companies.
Governor Eduardo Leite said earlier this week that initial calculations indicate that Rio Grande do Sul would need at least 19 billion reais ($A5.594b) to rebuild from the damage, which has extended into farm areas around the capital.
