Storm Ma-on barrels towards Hong Kong, Guangdong province

At 12:40pm (0440 GMT), the Hong Kong Observatory issued a strong wind advisory, with speeds up to 62kph (39 mph) expected. The storm, about 440km (270 miles) southeast of Hong Kong, will lash the city with heavy rains later Wednesday and into Thursday morning.

The Maritime Bureau of the Hong Kong-Zhuhai-Macau Bridge issued a typhoon-level II emergency response, closing it to shipping.

The ninth cyclone of the season, Ma-on is expected to generate waves of five to eight metres across the northern part of the South China Sea, according to local media. Storm surges are expected to affect several cities in Guangdong province, including Shenzhen, Chaozhou, Huizhou and Yangjiang.

The Shenzhen Meteorological Station upgraded the city's blue typhoon warning signal to yellow, and Zhongshan issued a yellow signal, suspending schools and child care classes throughout the city.

Shenzhen airport said it will suspend operation from 3:00am to 2:00pm on Thursday, according to a statement from its official weibo account, and the city's railway department suspended some train services between Wednesday to Friday, the local Southern Metropolis Daily reported.

China has a four-tier, colour-coded weather-warning system, with red representing the most severe warning, followed by orange, yellow and blue.

Ma-on is expected to gradually weaken after landfall, forecasters predicted.

The winds and rain could bring much-needed relief to southern areas assaulted by days of scorching heat, which has pressured China's national electricity grid, damaged crops and caused wildfires. Read full story

Though it will not directly impact Taiwan, the outer edges of Ma-on also brought heavy rain to southern and eastern parts of the island, with flights to the outlying Green Island and Orchid Island cancelled on Wednesday.