BEIJING, July 20 (Reuters) - Heavy rain is forecast to pound wide swathes of China, already reeling from flash floods and mudflows that have killed scores of people in recent days.

China's flood season, which usually lasts from May to September, has already killed hundreds of people this year and caused a 2-billion strong plague of rats fleeing rising waters in the south-eastern province of Hunan.

In the mountainous south-west province of Yunnan, 27 people were killed when a "mud-rock flow" triggered by torrential rain slammed into three tents where 74 workers were living near a dam, Xinhua news agency reported.

A flash flood on Wednesday afternoon in Luntai county, in the country's northwest Xinjiang region, killed at least five people at a mining camp, Xinhua said.

Since Saturday, heavy rains in Xinjiang's Changji region had destroyed 800 houses and nearly 10,000 hectares (38.6 sq miles) of crops and forced the relocation of more than 5,800 people, Xinhua said.

By Thursday, the death toll from storms in east China's coastal Shandong province had risen to 32, Xinhua said, citing the provincial civil affairs bureau.

Twenty-six people were killed in the provincial capital, Jinan, in collapsed buildings, submerged vehicles or by electrocution, the report said, after 180 millimetres (7.5 inches) of rain pounded the city in a few hours on Wednesday night, causing streets to be submerged under 2.5 metres of water.

The storm cut water and electricity for three hours and forced the evacuation of 112,300 people. Six remain missing, and economic losses have been estimated at 1.5 billion yuan.

Torrential rains will hit the southwest province of Sichuan, the Chongqing region, the Yunnan-Guizhou plateau, the central Huai river basin and lower reaches of the Yangtze river in the east over the weekend, forecasters said.

At least 37 people in Chongqing were killed in a rainstorm on Monday. Fourteen remained missing, Xinhua said.

Rising water-levels in the Huai river forced another 67,000 people from their homes in Anhui province on Thursday, the agency said.

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