The city's meteorological observatory issued an orange rainstorm alert, the second-highest warning level, on Wednesday afternoon as sheets of water inundated the city.

Almost a third of flights from Shanghai's two international airports were cancelled, the city's news service said, totalling around 640, with ferries and some train services also disrupted.

Authorities had evacuated 282,800 people to more than 1,900 temporary shelters across the city from Tuesday, state media said.

"I hope to return home only after the danger passes and the typhoon is gone... After all, it's much safer here," 57-year-old watermelon farmer Yang Xiaoping told AFP at a shelter in southern Fengxian district.

She was sitting in a large hall that normally functions as a community activity centre, about four kilometres (2.5 miles) from the coastline.

When AFP visited on Wednesday night, around 20 mostly elderly people were sitting on iron beds or gathered around tables to eat dinner, along with local community staff.

"Basically, we conduct an evacuation every year, sometimes even two or three times," said staff member Gong Huiyan.

"We also conduct annual drills, especially for typhoon and flood prevention, so the procedures are well-practised and guaranteed to run smoothly from top to bottom."

Yang said she had been in Zhejiang for almost two decades and had experienced typhoons every year.

"I haven't thought about leaving (this part of Shanghai) because I feel it's really good here. At the very least, the government... prioritises our safety," she said.

- Wave warning -

Co-May first made landfall in eastern Zhejiang province around 4:30 am Wednesday (2030 GMT Tuesday), bringing winds of 83 kilometres (52 miles) per hour.

Live shots from the coast showed waves overrunning seaside walkways, while broadcasts from the city of Ningbo showed residents sploshing through ankle-deep water.

Separately, China issued a tsunami warning for parts of the eastern seaboard after a magnitude-8.8 earthquake struck off Russia's Kamchatka Peninsula.

However, the warning was later lifted, according to CCTV.

Co-May was downgraded to a tropical storm before leaving the Philippines, then strengthened again over the South China Sea.

Its passage had an indirect link to extreme weather in northern China, Chen Tao, chief forecaster at the National Meteorological Center, told the state-run China Daily.

Torrential rain and floods in northern China have killed at least 48 people and forced the evacuation of tens of thousands this week.

"Typhoon activity can influence atmospheric circulation... thereby altering the northward transport of moisture," Chen said.

Natural disasters are common across China, particularly in the summer when some regions experience heavy rain while others bake in searing heat.

China is the world's biggest emitter of greenhouse gases that drive climate change and contribute to making extreme weather more frequent and intense.

But it is also a global renewable energy powerhouse that aims to make its massive economy carbon-neutral by 2060.