Downpours, hailstorms and a tornado battered parts of Yancheng City, destroying many houses, the city government said in a press release.
Extreme weather conditions were also reported from several townships in Funing and Sheyang counties in the suburbs of Yancheng.
Gales of 125 km per hour battered several outer townships of Funing County, while in Sheyang, the winds reached 100 km per hour.
Many houses collapsed in the gales, with 51 deaths reported and dozens of injuries.
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Witnesses said they saw huge trees falling and whole villages were levelled.
Victims were dragged from the ruins of their homes and rushed to hospital, state-run Xinhua news agency reported.
"I heard the gales and ran upstairs to shut the windows," said Xie Litian, 62, from Donggou township of Funing County.
Xie said he saw utility poles uprooted and his tractor was blown away.
"I was drowned in my own sorrow, until I heard moans for help from a neighbour buried in the debris of her home," he said.
Xie said at least three villagers he knew were dead.
Top officials of Yancheng City are leading rescue and relief efforts in the affected villages.
Yesterday the Ministry of Civil Affairs (MCA) said 42 people were killed and 25 missing in China's 10 provincial - level regions in heavy rains in the last five days.
More than 460,000 people were relocated and 321,000 are in urgent need of emergency relief after continuous rainfall in the 10 regions in southern part of China including Zhejiang, Jiangxi, Hubei and Sichuan, since June 18, the ministry said.
The seasonal rains, known as the "plum rains" or Meiyu-baiyu rains, cause heavy flooding in China every year, usually affecting the country for around two months beginning in late May.