Eugenio Giani, head of the central Tuscany region which includes Florence and Pisa, urged citizens to exercise "maximum care and attention", warning of "intense and persistent rain" during the day.

The fire service published images of cars partially submerged in water in the Sesto Fiorentino neighbourhood north of Florence's historic centre.

It said that by mid-morning on Friday it had received dozens of requests for help across the city.

Schools, parks and cemeteries in Florence and nearby Prato had already been closed Friday after an amber weather alert -- one down from the maximum red -- had been declared the previous day.

Giani said floodgates and expansion tanks were ready to be opened if necessary to ease the pressure on the Arno, the river which runs through Florence and Pisa to the sea.

To the northeast, authorities also issued a red weather warning for the region of Emilia Romagna, where devastating floods left 17 people dead two years ago.

Some rivers in the region, which includes the historic city of Bologna, were already swollen by previous downpours.

The municipality said on Friday morning the situation was "under control", but more rain was forecast that afternoon.