The recent hot spell in Italy has aggravated a water shortage caused by low rainfall since autumn 2016.
Furthermore, the arrival of large numbers of tourists chasing the European summer has increased the demand for water in the regions.
The drought has created an emergency for farmers and threatens the supply of drinking water.
The declaration of a state of emergency comes with the allocation of €8.65 million to help combat it.
Water shortages are also a major concern in many other parts of Italy, including the northern region of Piedmont, and the southern regions of Campania and Sardinia.
Rome Mayor Virginia Raggi on Thursday issued an order instructing residents in the Italian capital to limit water use for gardens, filling swimming pools and washing cars in an attempt to avoid a similar fate.
With ANSA