Police in central Chile used helicopters to airlift several residents to safety after rising floodwaters trapped them in their homes, the BBC reported.
Torrential rain caused the Mapocho River to burst its banks, flooding large parts of Talagante, about 35km (22 miles) south-west of the capital, Santiago.
Santiago recorded 74mm of rain in the first seven days of this month, making it the area's wettest October in 76 years, meteorologists said.
They warned that this year's unusually strong El Niño is likely to bring unusually wet weather, powerful winds and storms to the region during the Southern Hemisphere's spring.
Officials said one person had been found dead in a flooded underpass in San Bernardo, south of Santiago. The cause of death has not been confirmed.
In Talagante, police rescued people and pets living along the riverbanks who had been caught by the fast-rising water overnight. Dirt roads in the riverside community turned into rivers.
The community had not been evacuated ahead of the heavy rain, unlike during storms in July.
Climate experts have warned that the 2026-2027 El Niño is likely to cause major shifts in weather patterns around the world, intensifying droughts in some areas and floods in others. Central Chile is expected to receive above-average rainfall.