The blistering summer in southern Europe - dubbed the Lucifer heatwave - when temperatures soared to excess of 42 degrees has come to an abrupt end with torrential rain and flash flooding.

In Italy the downpours triggered flooding that killed at least six people n the Tuscan port of Leghorn, including a family of four who were trapped by rising water in a basement. Two persons were reported missing.

The Italian news agency ANSA said the bodies of a 4-year-old boy, his parents and his grandfather were found in the flooded basement of their two-family home. Before dying, the grandfather managed to save the boy's sister, state TV RaiNews24 reported.

Leghorn province's interior ministry official, Anna Maria Manzone, told Sky TG24 TV that by late Sunday afternoon two people were still missing. Sky reported that the six dead included two elderly people died a hillside hamlet on the outskirts of Leghorn.

"The city is literally devastated," said Leghorn Mayor Filippo Nogarin, adding that "a crazy amount of rain" pummeled the area in just a few hours.

Strong winds toppled trees and parked cars were nearly submerged by floodwaters that also left streets clogged with mud.

Nogarin appealed for volunteers to help. The city has a population of 170,000 and is a popular spot for travelers catching ferries to the islands of Elba and Sardinia.

Train service was interrupted in parts of the Tuscan coastal area along the Tyrrhenian Sea.

Flooding in Leghorn italy
A picture shows damages in the Livorno area, flooded after heavy rain, on September 10, 2017 STR/AFP/Getty Images

In Rome, which until recently had suffered through 3½ months of drought, the downpour quickly produced fast-moving streams in the streets. Several subway stations had to be closed.

City Hall urged residents and visitors to go outside only for urgent reasons and to avoid parks after Sunday morning thunderstorms lashed Rome. Possible hailstorms and strong winds were predicted throughout the rest of Sunday and Monday.