Italy's health ministry put ten cities at its highest or red heat risk level for the weekend, when temperatures are forecast to hit 40C in many parts of the country.
The alert will start on Saturday for Bologna, Bolzano, Brescia, Perugia, Torino, and will kick in on Sunday for Ancona, Campobasso, Florence, Perugia and Pescara, ministry said.
The red heat risk level (3) means "high-risk emergency conditions that will persist for three of more days in a row" according to the ministry.
"It indicates a heatwave with possibly harmful effects on healthy, active people, not just groups normally defined at risk like the elderly, young children and people with chronic illnesses.," the ministry said.
The heatwave comes after weeks of high temperatures and months of no rain that have caused drought in several areas and almost a billion euros of damage to agriculture.
The government on Thursday declared a state of emergency for the northern provinces of Parma and Piacenza in the Lombardy region due to a nine-month-long shortage of water.
The drought-hit central Tuscany and Sardinia regions have asked the government to call a state of emergency.
Despite Rome's underground springs, the city council is mooting a water-rationing plan and has told residents to curb their use of water for gardens, swimming pools and washing cars.