BEIJING, Aug. 2 (Xinhua) -- China's national observatory on Sunday issued a blue alert for Typhoon Hagupit, which is expected to bring gales and torrential rains to south China.

The typhoon, the fourth of this year, strengthened from a tropical depression Saturday evening and was observed at waters 800 km southeast of Cangnan County in east China's Zhejiang Province at 5 a.m. Sunday, with a maximum wind force of 64.8 km/h in the center, the National Meteorological Center (NMC) said.

The NMC expects the typhoon to move northwestward at a speed of 15 km to 20 km per hour before making landfall on the coastline between Zhejiang and Fujian Monday evening, where it will quickly weaken.

Meanwhile, Typhoon Sinlaku, the third one of this year, is heading northwestward at about 15 km per hour and is expected to land on the northern coast of Vietnam at around Sunday noon, the NMC said.

From Sunday morning to Monday morning, gales are expected to hit some sea areas east of Taiwan, parts of the East China Sea and some coastal areas of Guangxi Zhuang Autonomous Region, according to the NMC.

In the same period, regions including parts of Hainan and Guangdong provinces, as well as Guangxi Zhuang Autonomous Region will experience downpours, with some areas to see up to 140 mm of rainfall.

Typhoon Hagupit prompted China's State Flood Control and Drought Relief Headquarters to activate Level IV emergency response on Sunday against typhoons and floods.

The headquarters and the Ministry of Emergency Management stressed in a Sunday meeting the need to closely monitor the development of Typhoon Hagupit and to timely relocate vessels and people in areas likely to be affected, while calling for precautions against disasters like floods and urban waterlogging.

Two to three typhoons are expected to land in China this August, more than the average of 1.9 for the same month over the years between 1949 and 2019, according to Xiang Chunyi, a senior engineer with the China Meteorological Administration.

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