Freak storms and flash flooding following last week's heatwave in Italy claimed three lives this weekend, including a young woman caught up in a mini-tornado near Rome's Fiumicino airport.

The 26-year-old woman was driving home at around 2am Sunday when the mini-tornado lifted her car and sent it crashing against a railing.

The highly localised winds tore up trees and scattered debris across the zone it hit.

Further north, a 45-year-old Norwegian competing in an ultramarathon in the Dolomite Mountains died after being hit by lightning as he ran at 2,000 metres altitude on Saturday afternoon.

And on Sunday, near Arezzo, south of Florence in the northern Tuscany region, a 70-year-old man died after his car got caught by flash-flooding.

The emergency services found his body in a mud-filled canal.

Coldiretti, Italy's main agricultural organisation, said hail storms over the last 24 hours had caused millions of euros worth of damage across the country.

Worst hit was the Arezzo province in Tuscany, they said.

Orchards, as well as fields of tobacco, sunflowers and corn were completely destroyed, they said.