In 2012, China's northeastern provinces accounted for 23 percent of the country's grain production, 15 percent of its rice and 43 percent of its corn, official data showed.

"Corn in Northeast China is only harvested once a year, so a late ploughing means a shorter growing period, and this will affect yields," said Feng Lichen, president of Yumi.com.cn, a corn industry website.

"If the bad weather continues, the impact on this year's corn output will be huge," Feng said.

The local government and the Ministry of Agriculture said they are still assessing the losses caused by the rain, and they declined to reveal further details.

Meanwhile, analysts said that they feel "pessimistic" about the prospects of China achieving yet another bumper harvest.

And given the country's huge demand for corn, a reduced output would trigger price increases in the global food market.

"We expected to see a bumper corn harvest in the world this year, but if China suffers any losses in yields, corn prices in the global market will surge," said Ma Wenfeng, a senior analyst at Beijing Orient Agribusiness Consultant.

Ma also said the government could face growing inflation pressure in the second half of the year, as a reduced grain harvest would drive up food prices in the domestic and global markets.

"This will likely make the government tighten up monetary policies in the last few months of this year," Ma added.

China's grain output reached 589 million metric tons in 2012, the ninth consecutive year of increased grain harvests, according to the National Bureau of Statistics.

The country is the world's second-largest corn consumer after the United States. In 2012, corn imports to China jumped nearly two-fold to 5.2 million metric tons. Most of the imported corn came from the US.

Zhou Huiying in Heilongjiang and Han Junhong in Jilin contributed to this story.