More than a million people were evacuated in eastern China as Typhoon Dolphin, the most powerful storm to hit the country this year, came ashore over the weekend.

The typhoon crossed the coast near the city of Yuhuan in Zhejiang province at about 5.30pm local time on Sunday with sustained winds near the centre of 150kmph, equivalent to a category one hurricane, before making a second landfall at Wenzhou about an hour later, the National Meteorological Centre said.

Forecasters had issued a red alert, the highest of China’s four typhoon warning levels, but downgraded the system to a tropical storm on Monday morning.

Several areas of central and eastern Zhejiang were forecast to receive between 250mm and 500mm of rain, close to a full year's rainfall in London at the upper end.

Wenzhou, a city of nine million on the Zhejiang coast, moved more than 900,000 residents and opened over 1,000 emergency shelters. The nearby city of Taizhou evacuated some 390,000 people while Fujian province to the south moved 98,900 out of areas judged to be at risk, and Shanghai at least 30,300.

Nearly 1,500 flights were cancelled at Shanghai's two main airports and a further 270 at Hangzhou. Train services in the region were suspended and the port of Yangshan cleared its berths and moved more than 500 smaller vessels into shelter.

In Hangzhou, the Zhejiang capital, authorities waived parking charges across public spaces so drivers could move vehicles away from the wind and floodwaters, and closed the docks and sightseeing boats at West Lake, one of China's most visited sites, where trees were braced with props.

Fujian's maritime authorities suspended 55 coastal ferry routes, halted all 115 offshore construction projects, and moved 290 construction vessels to sheltered water.

The heaviest rain was moving north, with torrential downpours forecast through Wednesday across Shandong, Henan, Hubei, Anhui, Jiangsu, Zhejiang, and Shanghai, and as far as Tianjin and Beijing.

The water resources ministry warned that the Qiantang, Yong, Jiao, and Shuiyang rivers could flood badly and that smaller rivers in the worst-hit areas could rise above danger levels. People in parts of Zhejiang under a red warning for mountain torrents were told to follow local evacuation orders.

Chinese officials reported no casualties, though several state media outlets said a nine-year-old boy from Wenling in Zhejiang was missing after being swept into the sea.

Authorities, meanwhile, detained two people for spreading misinformation about the storm, according to state media. A 60-year-old man was accused of using AI to fabricate a video showing someone falling from a building in Shanghai while a 32-year-old was accused of re-editing footage posted by other users in a way officials deemed misleading.

By Monday morning, the storm had already crossed Japan's southern islands, where it injured seven people in Okinawa and cut power to more than 50,000 buildings. Among those hurt was a man aged over 100 who was blown over by a gust and hit his head, according to the prefectural government. It also brought heavy rain to the Philippines and northern Taiwan.

Dolphin’s arrival has pushed up temperatures hundreds of miles to the south. Air sinking on the outer edge of the system left Hong Kong reeling at 36.9C on Sunday, the highest temperature measured at the city observatory's headquarters since records began in 1884, above the previous record of 36.6C set in August 2017 days before Typhoon Hato struck.

A station at Sheung Shui in the north of the territory reached 39.8C and the observatory expected the heat to hold until Tuesday.

Dolphin travelled about 6,000km before reaching China, giving it a lifespan more than three times that of an average typhoon and an unusually large circulation, state broadcaster CCTV said. It hit two weeks after Typhoon Noul killed three people and damaged hundreds of homes in Guangdong in the south.

Scientists say a warming climate is making the most powerful typhoons and the most extreme heat more likely.