Almost one million people have been evacuated from coastal areas in anticipation of a typhoon carrying wind speeds of 107mph. Some 4in of rain has fallen since July 10.
Chan-hom is now heading north past the city of Shanghai.
The typhoon hit Taiwan and Japan earlier in the week, uprooting trees and injuring several people.
Chan-hom first hit Zhejiang province on an island near the city of Ningbo at around 16:40 local time, the National Meteorological Center said.
No deaths or injuries were reported in the region by July 11, state news agency Xinhua said.
One village, Laiao, received more than 16in of rain, it said.
The BBC’s John Sudworth in Shanghai says more than 400 flights have been cancelled there along with a number of public events, and the government has told people they should stay at home.
Dozens of flights were also cancelled in Zhoushan, Hangzhou, Ningbo and Wenzhou.
Zhejiang province has called its entire fishing fleet back to port.
Some 100 train services were also cancelled.
Chinese TV showed footage of coastal regions being battered by torrential rain as the typhoon neared.
Images from the region also showed flooded farmland.
China is well used to dealing with such storms, although this is possibly the strongest July typhoon to hit Zhejiang since 1949.
The highest red-alert warning remains in force, despite the storm being downgraded in category from Super to Strong.
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