Brazil’s President Luiz Inácio Lula da Silva said on Twitter he will visit the region.
Sao Paulo state government said in a statement that precipitation in the region has surpassed 600 millimetres in one day, one of the highest amounts ever in Brazil in such a short period.
Bertioga alone had 687 millimetres during that period, the state government said.
Governor Tarcisio de Freitas said in a statement he requested support from the army, which sent two aeroplanes and rescue teams to the region.
TV footage showed houses flooded with only the roof visible. Residents are using small boats to carry items and people to higher positions. A road that connects Rio de Janeiro to the port city of Santos was blocked by landslides and floodwaters.
The northern coast of Sao Paulo state is a frequent Carnival destination for wealthy tourists who prefer to stay away from massive street parties in big cities.