BEIJING - China's National Marine Environmental Forecasting Center (NMEFC) upgraded its warning for ocean waves triggered by Typhoon Dianmu to a yellow alert on Thursday, the third level on a four-color warning system.

Waves reaching a height of 6 meters will hit northern and central parts of the South China Sea and the Beibu Gulf from Thursday night through Friday.

Meanwhile, waves up to 3.5 meters in height will hit the coast of Guangdong province, Hainan province, and Guangxi Zhuang autonomous region.

Typhoon Dianmu arrived at the city of Leizhou, Guangdong, at 3:40 pm Thursday, whipping up ocean waves up to 5 meters in height in northern and central parts of the South China Sea and the Beibu Gulf.@ NMEFC also issued a blue alert for storms.

China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.