The most intense rain in half a century triggered flooding and mudslides that killed at least 95 people in southeastern Brazil, most of them in the Rio de Janeiro area, authorities said on Tuesday.
Flooding was so intense that authorities urged Rio residents to remain indoors and not venture downtown, where streets were impassable.
Some motorists abandoned their partially submerged cars, while others were stranded for hours inside stalled vehicles.
"All the major streets of the city are closed because of the floods," said Rio de Janeiro Mayor Eduardo Paes. "Each and every person who attempts to enter them will be at enormous risk."
Civil defense officials said most of the casualties were trapped in landslides in the hillside slums that ring Rio, a city of some 16 million people that will host the 2016 Summer Olympics.
Paes ordered schools closed on Wednesday for a second day in order to keep people off the streets. Separately, Rio state Governor Sergio Cabral decreed three days of mourning.
Flooding also wreaked havoc with air traffic, causing serious airport delays.
The Santos Dumont airport, which handles cargo flights, closed late Monday but re-opened on Tuesday. However at Rio's Antonio Carlos Jobim International Airport, most flights on Tuesday were delayed and several domestic flights were canceled.
In a neighborhood close to the mountain where Rio's iconic Christ the Redeemer statue is located, the local weather service said that rainfall was recorded as twice the amount normally registered for the whole month of April.
President Luiz Inacio Lula da Silva criticized decades of administrative malfeasance which allowed shoddy home construction in high-risk zones of the city's shantytowns.
The Brazilian leader was in Rio for ribbon-cutting ceremonies for a new health center, but the event was canceled by the rain, which made it nearly impossible to travel from one part of the city to another.
Officials for too long, Lula said, have closed their eyes to substandard construction, even on Rio's landslide-prone hills. Lula vowed that his government would work to improve the quality of construction in these areas.
Until the waters subside however, he said, there was little that could be done.
"All we can do is pray to God to hold back the rains a little, so that Rio can return to normal, and so that we can set about fixing the things in the city that need fixing," the Brazilian leader told local radio.
The heavy rain began during Monday's evening rush hour, catching workers heading home for the day off-guard.
After a brief afternoon lull rain on Tuesday again intensified after sunset, and officials warned that flooding could worsen on Wednesday.
The heavy rains in Rio followed equally heavy deluges in Sao Paulo earlier this year after the wettest summer in the region in more than six decades, officials said.
Those killer rainstorms across Sao Paulo state claimed dozens of lives.
Inmet, the national weather service, said the El Nino phenomenon -- which warms surface waters in the Pacific Ocean and is linked to rainfall across the region -- was to blame for those earlier floods.
Inmet, which has kept rainfall records since 1917, said that the Tuesday rainfall was the heaviest in the last 48 years.