A dog stands among the debris of a destroyed home in Huachipa, Lima, Peru, March 19, 2017. REUTERS/Mariana Bazo

The rapid and unusual warming of the waters off northern Peru has unleashed the deadliest rainfall the South American country has seen in decades.

Significant amounts of rain have fallen over relatively short periods of time in some parts of the Andean country in the latest iteration of a local El Niño, sending flash floods raging through city streets and across dry floodplains where people had built makeshift homes.

The downpours have overwhelmed riverbanks and caused mudslides.

"We've never seen anything like this before," said Jorge Chavez, a general in charge of organizing the government's response, according to Reuters.

"From one moment to the next, sea temperatures rose and winds that keep precipitation from reaching land subsided," Chavez said.

About half the country has been placed under a state of emergency to allow aid to get to the hardest-hit areas first, and in some areas on Peru's northern coast, small villages have been completely isolated by the deluge.

Intense rains and mudslides over the last week have wrought havoc around country and caught residents in Lima, a desert city of 10 million where it almost never rains, by surprise.