HONG KONG — Typhoon Noul will bring heavy to torrential rain across much of southern China for the next two days, authorities said, after sweeping through Guangdong province and neighboring Hong Kong with gale-force winds following its landfall on Sunday.

China issued its highest-level alert for flash floods in several provinces after the year's strongest typhoon forced the relocation of more than 700,000 people in Guangdong, authorities said.

The Ministry of Water Resources and the China Meteorological Administration jointly issued a red warning for flash floods. From Sunday evening through Monday evening, flash floods are expected in parts of Jiangxi, Hunan, Guangdong, Sichuan, Shaanxi, Gansu and southeastern Xinjiang.

Authorities warned residents to "pay attention to real-time monitoring, flood warning, and evacuation and risk avoidance prevention."

The warning came after Noul, the year's 12th tropical cyclone and China's third typhoon this month, made landfall in Huidong county at about 3:50 a.m., Sunday, provincial officials said.

Noul, which means the glow of sunrise or sunset in Korean, is expected to bring strong winds and heavy rain as it moves inland, state broadcaster CCTV said, with rainfall likely to persist until Tuesday. Some areas, including Fujian province, could see extremely heavy downpours.

Authorities urged local governments to closely monitor flood-prone areas, including mountain and river regions, construction sites, valleys and bridges.

The typhoon is weakening as it moves inland, Hong Kong's Observatory said, though southwesterly gales pounded parts of the Asian financial hub. All typhoon warning signals were cancelled on Sunday evening.

Overnight, the storm had passed within 80 km of Hong Kong.

Hong Kong airport authorities said flights would gradually begin resuming on Sunday afternoon, after operations were largely suspended for more than 12 hours.