More than a dozen people were missing in China on Tuesday after heavy rains and flooding struck swaths of the south, while the north baked under some of its highest temperatures this year.

State news agency Xinhua reported that four people were unaccounted for after a flash flood in Changji, in the northwestern region of Xinjiang, where torrential rains triggered landslides and clogged roads.

Landslides in Meizhou, in southern Guangdong province, on Monday killed five, left 15 missing and another 13 "trapped" by early the next morning, state broadcaster CCTV said.

Footage from state broadcaster CCTV showed upturned cars and damaged buildings near Meizhou, with residents in rubber boots picking through muddy, debris-laden streets to salvage their belongings.

Other images showed sections of highway swept away by landslides and rescue workers in orange lifejackets steering dinghies through the floodwaters to reach trapped villagers.

Chinese President Xi Jinping called for emergency workers to "make every effort to respond to disaster situations and do a good job of relief and rescue work to combat flooding and drought", Xinhua reported Tuesday.

He instructed rescuers to "guarantee the security of people's lives and property, and overall social stability", Xinhua said.

In the neighbouring province of Fujian, more than half a million people have been affected by "continuous rainfall and flooding", state media said.

Flooding has also hit the southern and central provinces of Guangxi and Hunan.

China's north is wilting under some of the year's hottest weather.

The mercury was expected to soar to up to 39 degrees Celsius (102 degrees Fahrenheit) in the capital Beijing and the surrounding areas of Tianjin and Hebei on Tuesday, the National Meteorological Centre said.

Authorities have also moved to offer drought prevention and disaster relief in seven provinces across China's north, east and centre.

China is enduring a summer of extreme weather, which scientists say is made more common by climate change.

Greenhouse gases, of which China is the world's biggest emitter, are a key contributor to climate change.