The storms, which battered Minxian county on Thursday, had affected 358,000 people. Nearly 30,000 people were evacuated after the storm.
Eighteen people remained missing in the county, a disaster-prone area in Gansu province. Another 87 people had been hospitalised, official Xinhua news agency reported.
Roads were blocked, houses collapsed, farmland destroyed, power supply and telecommunications service disrupted by the extreme weather, according to Xu Guangyao, director of the Minxian county civil affairs bureau.
A total of 950 tents, 1,270 beds and relief supplies had been sent to the disaster-stricken area, but the local residents were still in need of relief supplies, he said.
The stormy weather lasted just about an hour but wreaked havoc in all of the county's 18 townships.
Minxian is a mountainous county in the city of Dingxi with a population of 450,000.
It is located 150 km from Zhouqu county, where a rain-triggered mudslide killed more than 1,500 people in August 2010.