Rescue teams searched overnight and into Thursday morning for people feared to have drowned during the flash floods, caused by what the mayor said was the most violent rainstorm since “at least 1790”.
Over one metre of rain fell in under two hours, leaving cars submerged in parts of the city centre.
Italian media initially reported that two people had drowned in the flooding, following an eyewitness report of a couple trapped in their car in a flooded underpass.
But local police have since stated that they have't received any reports of missing persons in the area.
There are no confirmed deaths or serious injuries due to the flooding, firefighters confirmed early on Thursday morning, adding that they were continuing to search for people in the underpass while pumping out floodwater.
However, two small children were reportedly taken to hospital with suspected hypothermia after being trapped in a car with their parents in the same submerged underpass.
Videos published on social media showed people caught in the rainstorm abandoning their submerged vehicles and swimming through deep water and mud, while recycling bins and other objects floated down flooded streets.
This type of sudden, violent rainfall is commonly called a bomba d'acqua, or “water bomb”, in Italian.
However this particularly heavy rainstorm was the worst the city has seen in over 200 years, Palermo's mayor said.
“Over a metre of rain fell in Palermo in less than two hours,” mayor Leoluca Orlando told Italian news agency Ansa
He said it was “the most violent rainstorm in the history of the city since at least 1790, equal to that which usually falls in a year.”
He said the city had no warning ahead of the violent rainfall, and the civil protection agency had not issued any weather alerts for the area.
Orlando said that if the city had received advance warning, “procedures would have been activated which, despite the extraordinary nature of today's events, could have mitigated the risks.”