Flash floods in La Plata, the capital of Buenos Aires province, have left close to 60 people dead and forced 1,500 to evacuate their homes.
People drowned while trapped in their cars and some were electrocuted as the water rose at an alarming rate.
The President of Argentina Cristina Fernandez visited the flood zone and promised state aid.
Local media report that 400 millimeters of rain fell in two hours flooding low-lying areas of La Plata and surrounding districts.
“No structure could handle the rainstorm. People spent the night on roofs getting wet, families, small children, people in wheelchairs that had water up to their waists. A disaster, a disaster,” said one witness.
The Argentine Red Cross has set up emergency assistance areas to help those hit by the floods.
Weather forecasts predict more rain to come.