A sudden and abnormal warming of Pacific waters off Peru has unleashed the deadliest downpours in decades, with landslides and raging rivers sweeping people away, clogging highways and destroying crops. At least 75 people have died, with another 20 reported missing, and more than 70,000 made homeless as the rainy season has dumped 10 times as much rain on Peru than normal.

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A woman is helped to cross a flooded street after the Huaycoloro river burst its banks, sending torrents of mud and water rushing through the streets of HuachipaGuadalupe Pardo/Reuters

A state of emergency has been declared in about half of Peru after flooding and landslides, mostly in the north where rainfall has broken records in several districts. The intense rains, raging rivers, mudslides and flooding being experienced in the country are the worst seen in two decades, Peruvian authorities said.

Even Peru's capital city of Lima, where a desert climate seldom leads to rain, police had to help hundreds of residents cross flooded roads by sending them one-by-one along a rope through choppy waters after a major river overflowed. Some residents left their homes with just a single plastic bag carrying their belongings.

The rains have overwhelmed the drainage system in the cities along Peru's Pacific coast and the health ministry has started fumigating around the pools of water that have formed in the streets to kill mosquitoes that carry diseases like dengue. In the Lambayeque region, 22 inmates at a juvenile detention centre took advantage of the rains to escape. And in the city of Trujillo, rains flooded a cemetery with the waters carrying bones through the streets.

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Rescue workers help a woman to cross a flooded area of Huachipa, east of LimaChris Bouroncle/AFP
Peru landslides floods inundacin imagenes
A volunteer cleans a flooded home, after rivers breached their banks in Cajamarquilla, LimaMariana Bazo/Reuters
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A muddy dog is seen among flood debris in the remains of a home Huachipa, LimaMariana Bazo/Reuters
Peru landslides floods inundacin imagenes
Volunteers give clothes to victims, after rivers breached their banks due to torrential rains, causing flooding and widespread destruction in Cajamarquilla, LimaMariana Bazo/Reuters
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A man sits with his belongings after flooding and widespread destruction in Huachipa, LimaMariana Bazo/Reuters
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People try to cross the Rimac River in Huachipa, LimaMariana Bazo/Reuters
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Flood survivors lie on a mattress outside what is left of their home in Huachipa, LimaGuadalupe Pardo/Reuters
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The Rimac River rages past destroyed homes in Huachipa, LimaMariana Bazo/Reuters
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A man walks next to his destroyed home in Cajamarquilla, LimaMariana Bazo/Reuters
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A woman tries to walk through thick mud in a flooded market in Huachipa, LimaMariana Bazo/Reuters
Peru landslides floods inundacin imagenes
A man cleans his house after a massive landslide and flood in the Huachipa district of LimaGuadalupe Pardo/Reuters
Peru landslides floods inundacin imagenes
A man cleans his home in Huachipa after rivers breached their banks due to torrential rains, causing flooding and widespread destructionMariana Bazo/Reuters
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Police carry the body of a victim of a massive landslide and flood in Trujillo, northern PeruDouglas Juarez/Reuters
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Rescuers help residents cross a flooded street in the town of Huarmey, 300 kilometres north of LimaChris Bouroncle/AFP
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Residents wade through muddy water on a street in Huarmey, 300 kilometres north of LimaChris Bouroncle/AFP
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A bulldozer removes mud in the town of Huarmey, 300 kilometres north of LimaChris Bouroncle/AFP
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Local residents stand on a road damanged by the flash floods in HuachipaErnesto Benavides/AFP
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Local residents affected by the flash floods sit outside tents set up by volunteers and authorities in HuachipaErnesto Benavides/AFP
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The railway line that follows the Rimac River is severely damaged by rising water and flash foods in the town of ChosicaChris Bouroncle/AFP
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The Rimac River sweeps through the town of Chosica, at the foot of the Andes mountains east of LimaChris Bouroncle/AFP
Peru landslides floods inundacin imagenes
A section of the railway line that was severely damaged by the raging river rushing through the town of Chosica, east of LimaChris Bouroncle/AFP
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Llamas graze along the railway line that follows the raging Rimac River in the town of Chosica, at the foot of the Andes mountainsChris Bouroncle/AFP
Peru landslides floods inundacin imagenes
Firefighters help a child to cross a flooded street in Huachipa, east of LimaChris Bouroncle/AFP
Peru floods
Residents of a populous district of Lima remove from their house mud, debris and water left by a flash floodErnesto Benavides/AFP
Peru floods
A bulldozer removes mud in the town of Huarmey, 300 kilometres north of Lima, PeruErnesto Benavides/AFP
Peru floods
Local residents try to cross a flash flood in Huachipa district, on the east side of Lima, PeruErnesto Benavides/AFP
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Debris left by flash floods in Huachipa district, east of Lima, PeruErnesto Benavides/AFP
Peru floods
A man walks past a vehicle stuck in the mud left by flash floods in Huachipa district, east of Lima, PeruErnesto Benavides/AFP
Peru floods
General view of the damage caused by flash floods in Huachipa district, east of Lima, PeruErnesto Benavides/AFP

The Andean nation is bracing itself for another month of flooding. A local El Nino phenomenon, the warming of surface sea temperatures in the Pacific, will probably continue along the northern coast at least through April, said Dimitri Gutierrez, a scientist with Peru's El Nino committee.

Coastal El Niños in Peru tend to be preceded by the El Niño phenomenon in the Equatorial Central Pacific, which can trigger flooding and droughts around the world, said Gutierrez. But this year's event in Peru has developed from local conditions. The US weather agency has put the chances of an El Nino developing in the second half of 2017 at 50-55%. Some scientists have said climate change will make El Niños more frequent and intense.

While precipitation in Peru has not exceeded the powerful El Niño of 1998, more rain is falling in shorter periods of time – rapidly filling streets and rivers, said Jorge Chavez, a general tasked with coordinating the government's response. "We've never seen anything like this before," said Chavez. "From one moment to the next, sea temperatures rose and winds that keep precipitation from reaching land subsided."