A severe storm hit northern Argentina and parts of Paraguay on Wednesday.

The worst hit were Corrientes and Resistencia, neighbouring cities lying on either side of the Parana River.

Corrientes was hit by 100mm of rain in just two hours, while Resistencia was hit by the same amount of downpour in just 40 minutes.

By the time the storm eased, Resistencia had reported a total of 224mm of rain, far exceeding the 174mm average rain it gets in the entire month of January.

The deluge led to major flooding, halting the traffic and submerging cars.

Homes were inundated, forcing thousands of families to evacuate and seek refuge in emergency shelters set up in community centres across the two cities.

Gusts packing 90km an hour accompanied the storm, tearing down trees and power lines, prompting authorities in Resistencia to urge people not to leave their homes for fear of electrocution.

An alert remains in force across the region, with the risk of the storm extending south into Uruguay on Thursday.

Experts say the flooding could have been caused by a higher than usual temperature in the Pacific. If it rises further, an El Nino event will be declared. El Nino often causes floods in northern Argentina.

If the extra warmth of the Pacific resulted in the storm, there could be more rains and flooding in the coming days.