Hurricane-force winds, freak hailstorms, pounding rain and a tornado killed 78 people in China's eastern province of Jiangsu on Thursday and injured nearly 500 others, Xinhua reported.
Whole villages were levelled and huge trees felled when winds of up to 125 kilometres (77 miles) per hour struck around Yancheng city, China's official news agency said.
Some 200 people were left critically injured by the storms and the worst tornado in half a century, which reduced buildings to rubble.
Photos of the scene showed dazed residents near the remains of houses surrounded by tangled telephone wires, splintered wood and toppled poles.
"It was like the end of the world," said Xie Litian, 62, from Donggou township in Funing County, describing how all the other houses in his neighbourhood had been destroyed.
"I heard the gales and ran upstairs to shut the windows," he told Xinhua.
"I had hardly reached the top of the stairs when I heard a boom and saw the entire wall with the windows on it torn away."
President Xi Jinping ordered "all-out rescue efforts" after what Xinhua said was one of the worst disasters ever to hit Jiangsu.
Citizens in Yancheng used social media to offer help to those affected, from medical assistance to using heavy lifting equipment for free.
Crane operator Xiang Shanfeng said he had pulled dozens of people from rubble during the day after posting his number on messaging service WeChat.
"The losses were astonishing," Xinhua quoted him as saying.
Many parts of China have been lashed by torrential rains this week as summer rainstorms have been heavier than usual, causing damage across the country.
Flooding is common during the summer monsoon season in the south of China, but rainfall has been particularly heavy this year.
In the centre of the country, heavy floods have killed 22 people and displaced 197,000, state media said on Monday.
Eight people were trapped in a flooded coal mine in southwest China's Guizhou province, Xinhua reported.
Direct economic losses from the floods hit nearly 2.7 billion yuan ($410 million), state media said.
Vice premier Wang Yang said days earlier that China faced volatile weather conditions due to the influence of the El Nino weather system.