Water levels began receding, however, in Venice, which at the weekend saw its sixth-worst flooding since records began in 1872.
The two men and one woman who died in Tuscany were local electricity workers. Their deaths brought the number of fatalities caused by flooding to four.
The deluge has caused major damage to homes and shops as well as thousands of acres of farmland. It also forced officials to close the A-1 highway in parts of Tuscany, where it runs close to rivers.