A severe drought in several European countries is threatening crops and has caused Italy to declare a state of emergency in its northern and central regions a day after France imposed water rationing. Farmers in Italy, France, Germany, Austria and Switzerland say it is the worst drought they have seen.

Italy acted on Thursday even as it was beginning to rain in the worst affected areas, saying that the forecasted rain would not make up for the rain deficit in the region.

The lack of rain in many parts of Europe has lowered river levels to historic lows. That includes Italy's Po River, which runs west to east across northern Italy. It feeds the fertile Po Valley where about a third of Italy's food is grown.

The German Weather Service said that April broke records kept since 1901 as the hottest and driest month. Italian officials say this winter was the warmest on record in 200 years.

Italy's warm winter caused the level of the Po River to start the Spring season low because there was very little snow in the Alps to melt and runoff into the river. That combined with a warm dry spring brought the river levels down further.

The Po Valley is also heavily industrialized and about 15 percent of Italy's electricity is from hydropower plants. Officials said the drought might force industries to shut down.

In Italy, sugar and rice crops are threatened. The drought has also dried up feed for dairy cows that produce milk for such classic Italian cheeses as Grana Padano and Parmesan and feed for hogs that are used for Parma and San Daniele prosciutto.

In Germany, wheat, rye, barley, rapeseed, strawberries and lettuce crops are threatened by the drought. Dry meadows mean farmers have to buy fodder for cattle, which drives the price of milk up.

In Switzerland, the drought threatens the dairy industry, a large exporter of cheese and premium butter to the United States, that is suffering a lack of hay and meadows for cows.