Dark clouds gather over the mountains in Zhaoqing, southern China's Guangdong province. File/Reuters

Major rivers, waterways and reservoirs in China's Guangdong province are threatening to unleash dangerous floods, forcing the government on Sunday to enact emergency response plans to protect more than 127 million people.

Calling the situation "grim", local weather officials said sections of rivers and tributaries at the Xijiang and Beijiang river basins are hitting peak water levels that only happen once in 50 years, according to state broadcaster CCTV news on Sunday.

Massive flooding is expected at the Beijiang basin, CCTV said quoting China's water resource ministry, prompting it to raise an emergency advisory.

Guangdong officials urged departments in all localities and municipalities to begin emergency planning to avert natural disasters and promptly disperse disaster relief funds and materials to ensure affected people have food, clothing, water and a place to live.

The province has seen torrid downpours for several days and strong winds due to severe convective weather, which has affected several parts of China over the past few weeks.

A 12-hour stretch of heavy rain, starting from 8 p.m. (1200 GMT) Saturday, battered the central and northern parts of the province in Zhaoqing, Shaoguan, Qingyuan and Jiangmen.

Almost 20,000 people have been evacuated in Qingyuan, according to state media, and some power facilities in Zhaoqing were damaged, cutting power to some places.

Reuters