BEIJING, July 4 (Reuters) - China's weather bureau warned on Thursday that a prolonged heatwave forecast in the country's eastern, central and southern regions in July may hit production of rice and cotton, as extreme weather continues to threaten its food production.

The China Meteorological Administration (CMA) said it expected temperatures in most areas across China to be relatively high over the next few months, signalling a second consecutive summer of extreme heat.

"It is necessary to guard against the risk of yield reduction of cotton, early rice and late rice caused by high temperature and heat damage," Jia Xiaolong, the CMA's deputy director, said at a briefing.

Summer temperatures in regions including Zhejiang, Jiangxi, Hunan, Fujian, Guangdong, Guangxi, Gansu and Ningxia are expected to be 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) above normal, the CMA said.