Flood control and disaster relief workers across Guangdong province have gone all out to eliminate safety hazards as the province in southern China braces for possibly the heaviest torrential rain this year. The downpours began on Wednesday.

As of Thursday afternoon, five red alerts for torrential rain, the highest level in the four-tiered warning system, are still in effect in Taishan, a county-level city in Jiangmen, and the cities of Heyuan, Zhuhai, Zhongshan and Shenzhen.

Yellow and orange alerts had already been issued, covering almost the entire province, according to the Guangdong Meteorological Service Center.

Affected by the spate of downpours, four rivers including the Bao'an, Paitan, Yonghan and Pajiang in Guangdong have exceeded flood alert levels, according to the hydrological authority.

Residents living in areas at risk have been evacuated to safe areas. In Aotou township of Conghua district, Guangzhou, the capital of Guangdong, a total of 4,262 residents have been evacuated.

Due to the rainstorms, dozens of parks, scenic spots and cultural attractions in the province have been closed since Wednesday to ensure public safety.

Authorities in cities including Guangzhou, Foshan, Zhuhai, Zhongshan, Jiangmen, Yangjiang and Zhaoqing suspended classes in kindergartens, primary and high schools from Wednesday to Thursday. Shenzhen canceled classes in all kindergartens and primary and secondary schools from Thursday to Friday.

Some trains between Guangzhou and Beijing, Jiangmen and Zhanjiang, Guangzhou and Zhuhai, Guangzhou and Shenzhen, and Hangzhou and Shenzhen have been suspended or had their timetables adjusted from Wednesday to Friday, according to Guangzhou Railway Group.

Shuttle bus services from Hong Kong to Zhuhai across the Hong Kong-Zhuhai-Macao Bridge, the longest open-sea fixed crossing in the world, were suspended from Wednesday afternoon, and won't resume until Saturday.

Passenger ferries between Shenzhen and Zhongshan were also canceled from Wednesday to Friday.

Torrential rains were forecast to hit Shenzhen on Thursday and Friday, especially in Bao'an, Nanshan, Futian and Yantian districts, Dapeng New Area and the Shenzhen-Shanwei Special Cooperation Zone.

The city's meteorological authority issued a red alert on Thursday morning, which took effect across the entire city area and called on residents to stay indoors.

When the red alert took effect, employers arranged for staff to leave work early or stop work, according to the local flood control headquarters.

All of Shenzhen's forest and country parks were closed to the public starting Thursday until further notice.

"The public area in my residential community was full of water, after it rained in the early morning, but without strong winds," said Zeng Xuanxin, a 37-year-old mother in Shenzhen.

The local flood control headquarters has directed 45,000 registered staff responsible for managing the risk of flooding across the city to remain vigilant and monitor the situation closely.

Zhang Dong, chief weather forecaster at the Guangdong Meteorological Service Center, said strong southwestern warm and humid air coming in from the coast, coupled with low vortex shear, caused this front of heavy rainfall.

"It doesn't belong to the dragon boat rain, which often refers to heavy downpours each year between May 21 and June 20, which are around the time of the Dragon Boat Festival," Zhang said.

Torrential rain is forecast to continue in most parts of Guangdong on Friday, according to the Guangdong Meteorological Service Center.