The municipal weather service announced a red alert -- the highest in a four-tier system -- forecasting heavy rain from noon on Monday until Tuesday morning.

Most parts of the city are expected to see 100 millimetres (four inches) of rain during a six-hour period overnight, but outlying areas could experience between 150mm and 200mm, authorities said.

"There is an extremely high risk of flash floods, mudslides, landslips and other natural disasters in mountain areas," the Beijing government said on an official social media account.

"Citizens are advised not to go outside unless necessary," it said.

Tens of thousands of people in northern China were evacuated as torrential rains wreaked havoc in parts of the north since last month.

Beijing was struck hard last week, when floods in its northern suburbs killed at least 44 people and left nine missing, according to official figures.

Some 31 fatalities occurred at an elderly care centre in Miyun district, prompting a local official to admit "gaps" in disaster readiness.

Residents in flood-hit areas told AFP reporters at the scene that they had been surprised at the speed with which the rushing water inundated homes and devastated villages.

The city water authority on Monday again listed Miyun as highly vulnerable to flooding, alongside Fangshan, Mentougou and Huairou districts, according to state news agency Xinhua.

Natural disasters are common across China, particularly in the summer, when some regions experience heavy rain while others bake in searing heat.

China is the world's biggest emitter of the greenhouse gases that drive climate change and contribute to making extreme weather more frequent and intense.

But it is also a global renewable energy powerhouse that aims to make its massive economy carbon-neutral by 2060.