BEIJING, June 11 -- As farmers in north China harvest their wheat, and rain has battered south China, the distinct weather fronts have taken as a harbinger of El Nino.

The wheat harvest is almost finished in the major producing provinces of Henan and Anhui, and is in full swing in Shandong and Hebei.

Wheat output is projected to be high this year in Henan, the country's top producer of the grain, thanks to timely rainfall, said Huang Wei, from the provincial agricultural department.

Last summer, Henan reaped a record harvest of 33 million tonnes of wheat.

However, autumn harvest yields may not fare so well due to the uncertain weather conditions brought about by El Nino, an unusual warming of the sea's surface in the Pacific Ocean. The weather pattern can cause uncertainties the agricultural sector could do without.

El Nino will continue to strengthen this summer and will last until the autumn, according to China's National Climate Center earlier this month.

It is at a medium strength currently and is likely to reach a strong magnitude, said the center, which forecast more-than-usual rainfall in the country's southern and eastern areas in the summer months, while the northern region will likely face droughts in summer and autumn.

Between May 25 and 31, the temperatures of the water on the surface of the ocean along the equator was 1.4 degree Celsius higher than normal, according to monitoring by the center.

Though hard to predict its development, El Nino will reach its peak in winter with a magnitude possibly nearing that of the 1997-1998 occurrence when many of China's rivers in northeast broke their banks, according to Bueh Cholaw, a climate researcher with the Chinese Academy of Sciences.

In May, the accumulative precipitation in the south was 50 percent more than that of the normal years.

The Ministry of Agriculture warned that adverse weather could cause crop damage to rice in south China and grains in the north.

To guard against possible damage, the ministry urged agricultural authorities to maintain vigilance and to disseminate effective disaster relief and scientific guidance to farmers.

China's total grain output grew for the 11th consecutive year, reaching 607 million tonnes in 2014. This year, the grain output target was set at 550 million tonnes.

China has invested in improving agricultural facilities to better brace against natural disasters.

Henan, for example, now has 2.4 million hectares of high-standard cropland and plans to increase this by a further 600,000 hectares this year.

Quality cropland can deal with both drought and flood, said Huang, the Henan official in charge of grain plantation.

Agricultural officials in Hunan, Hubei and Jiangxi, which have been repeatedly battered by downpours since May, are organizing technical experts to help farmers plant crops in flood-devastated croplands.

Governments at different levels in Jiangxi have earmarked nearly 100 million yuan (16.3 million U.S. dollars) to agricultural sector disaster relief this year.

With the possibility of extreme weather, preventive and relief measures should be prepared, and infrastructure improved to guarantee grain output, according to experts.