Three employees of Italian energy company ENEL died Monday night when the bridge they were driving over collapsed from torrential rains that overwhelmed the Albegna River in Tuscany, the Italian news agency ANSA reported.
A 73-year-old man died in the same area Monday when his car was swept off the road by flood waters from the Chiarone River.
In Venice, tourists wearing bathing suits took pictures of themselves in waist-high water.
Tuscany has been particularly affected by the flooding.
Damage to the central and northern parts of Italy caused by the rain will cost more than $635 million to repair, the national agricultural confederation estimated.
Wine and olive oil production has been severely hampered by storms and mudslides, the confederation said.
The area was still recovering from heavy snowfall at the start of the year that was followed by a long dry spell this summer.
Florence and the surrounding area are under a storm alert until midnight Tuesday, reported Agenzia Giornalistica Italia.
While the Arno River, which flows through Florence, was reported to be subsiding, the Tuscan Regional Authority said more thunderstorms were expected.