"I don't understand why that happened," he said, standing ankle-deep in muddy water. "All our team members have set aside everything related to their ordinary work and have come to help. I don't think that in any way I am outstanding."

According to Blue Sky Rescue, Yu is one of the 856 members who have been at the forefront of flood relief work in Henan since 4 pm on Wednesday. The organization, which is headquartered in Beijing, is the country's first registered nonprofit volunteer outfit.

Just 24 hours earlier, Zhengzhou, the Henan provincial capital, was hit by record hourly precipitation of up to 201.9 millimeters.

Liu Daqing, a member of Blue Sky Rescue in Shandong province, who works for an insurance company, said his 87-strong team comprising members across the province started to gather around midnight on Tuesday soon after receiving a request to reinforce flood control efforts in Henan.

Traveling in cars, the group members quickly joined evacuation work after arriving in Xinmi, a county in Zhengzhou, at about 9 am amid torrential rain. After the situation improved in Xinmi, the group headed to Xinxiang, one of the hardest-hit cities, at 4 am on Friday.

"We are currently stationed at a school, living in students' dorms. We have nothing but cushions on our beds," Liu posted.

Rain and flooding eased in urban areas of Xinxiang on Saturday as the water level dropped. However, floodwaters up to 2 meters deep continued to cause havoc in many rural areas. One car broke down as the team members sought a return route from an evacuation mission on Saturday in an area inundated by flooding.

Despite the grave situation, Liu's teammates are continuing to apply to go to Henan.

Liu said at least 1,400 fellow volunteers nationwide have registered with Blue Sky Rescue's temporary headquarters in the province.

The organization is one of at least 103 civilian rescue teams that arrived in the province on Wednesday, according to China Philanthropy Times, quoting a center set up to coordinate the work of civilians in Zhengzhou.

It is not the first time that the nation's civilian rescue teams have taken part in flood disaster relief work.