Environment Minister Alfonso Pecoraro Scanio said he would ask a cabinet meeting on Tuesday to declare a state of emergency.

"The drought crisis must be dealt with without delay and in a rational way," Pecoraro said.

Among the measures considered is filling up the Po river, whose levels have been dropping sharply in the past few weeks, with controlled water flows from big lakes and reservoirs in the Alps, even though that is not expected to bring it back to normal levels.

To minimise the risk of blackouts caused by millions of people cranking up air conditioners, the government may also implement accords that allow supplies to some industrial clients to be temporarily interrupted, and raise electricity imports.

Around 15 percent of Italy's electricity is produced from hydro generation. Water supplies are also essential for colling down thermoelectric plants.

Drought fears intensified after the Po fell on Sunday to 6.53 metres (21 ft 5.0 in) below its normal level in the northern town of Pontelagoscuro, having dropped by 80 centimetres in a week. The Po region accounts for about one third of Italy's agricultural production.

At one site, the nearby Lake Garda was 50 centimetres below its average of the past 50 years, although the levels of other lakes were not worrying for now, Italy's biggest farmers association Coldiretti said.

Italy's hottest winter in 200 years meant snowfall was light in the Alps, with little snow-melt to swell the Po. Then a hot, dry spring set in, with temperatures over the past few days approaching levels usually seen in June.

Farmers are looking ahead to the beginning of the farm irrigation season next month with concern.

"We are very worried for this summer because there has been very little rain during the winter and there is insufficient water in the mountains," Fabrizio Ferro, a farmer in the city of Rovigo, on the Po delta, told Reuters.

"Some of my colleagues this year have even decided to abandon the cultivation of rice because they can already see the water in the Po is much lower," he said.

Flowing for 650 kms (406 miles) from the Alps to the Adriatic Sea, the Po has made the region it crosses Italy's most fertile agricultural lands and helped turn the north into the country's industrial heartland.

Its delta of 70,000 square km houses thousands of rice, maize, tomato and melon cultivators. "The water availability of the river determines the survival of whole agricultural sectors such as rice and sugar," Coldiretti said.