The body of 56-year-old security guard Luigi Albertelli was found near his car in the Ponte dell'Olio area, Ansa reported on Monday.
Two brothers, who may have been travelling on a motorway that was hit by flooding, are still missing.
Flooding also hit nearby towns as well as several cities in the Veneto region, while a motorway near Cortina was blocked due to a 30-metre landslide.
Torrential rain also caused flooding in the Ligurian port city of Genoa, many parts of which were wrecked by flooding less than a year ago after the Bisagno River broke its banks.
In mid-August, two people were killed when storms swept through Italy.
Earlier in the month, three people in the Veneto region died in landslides. A week later, the government pledged to spent €1.3 billion on flood prevention and safety measures.
Environment Minister Luca Galletti said at the time that €654 million had already been made available to the cities worst-hit by flooding, while adding that an agreement would be made with unions to allow around-the-clock work on the most critical projects.
A series of floods and landslides across northern and central Italian regions between October and December last year also claimed thirteen lives.
The floods in Genoa last October were the worst to strike the city since 2011, when seven people, including two children, lost their lives. But money allocated to build flood safety measures at the time was never spent, due to legal wrangling.