The extreme conditions have resulted in at least 10 deaths and have left 33 people missing.
Heavy rainfall began around 6pm on Thursday, triggering flash floods in Yuzhong, Gansu province, and leaving about 4,000 people stranded.
One mountainous area in Yuzhong County saw up to 195mm (7.7in) of rainfall since Thursday evening – around half of the 300mm to 400mm it typically gets in an entire year.
Ankle-deep muddy water could be seen flowing down a hillside road, bordered by trees that had been torn from the ground.
“The top priority must be to make every possible effort to search for and rescue missing people, relocate and resettle people under threat, minimise casualties, and restore communications and transportation as quickly as possible,” President Xi said.
He warned local authorities against falling into “complacency and negligence” amid the recent surge in extreme weather events.
Yuzhong lies amid gullies and hills composed of wind-blown silt on one of the largest loess plateaus in the world. This loose soil structure makes the area prone to flash floods and landslides, as it becomes unstable when soaked in water.
Heavy rains and flooding have killed at least 60 people across northern China including the capital Beijing since late July.
The National Development and Reform Commission announced on Friday that it has allocated 100 million yuan (£10.4m) to support rescue efforts in Gansu following the disaster.
Since April, China has pledged at least six billion yuan (£622m) in disaster relief funding.
Meteorologists have linked the extreme weather events in China’s north and south to climate change.
