BEIJING, Aug. 26 (Xinhua) -- Beijing upgraded its emergency response for flood control from Level III to Level II at 4:30 p.m. Tuesday, warning of citywide downpours, according to local meteorological authorities.

From Tuesday night to Wednesday night, some areas could receive over 70 mm of rain within six hours or more than 100 mm within 24 hours, said the Beijing meteorological observatory.

The observatory issued an orange alert for rainstorms citywide at 4:00 p.m. Tuesday -- while red alerts have been issued for the suburban districts of Fangshan, Mentougou, Huairou, Changping and Yanqing.

As of 5:30 p.m. Tuesday, the city's water and meteorological authorities jointly issued orange warnings for mountain torrents, noting that the districts of Fangshan, Mentougou, Changping, Yanqing and Haidian are all at high risk of mountain torrents, while mountainous areas in other regions of the city face a relatively high possibility of mountain torrents.

Lei Lei, chief forecaster at the observatory, said the rainfall process is expected to have a long duration, large cumulative rainfall and a wide impact range. Daytime on Wednesday will be the main precipitation period, adversely affecting morning and evening commutes.

The public is advised to stay away from dangerous areas such as mountains and river channels, suspend outdoor activities in mountains and waters, and take precautions against mountain torrents, as well as to refrain from being under or near tall buildings, billboards, temporary structures and large trees -- as strong winds will accompany the rainfall.

On Tuesday afternoon, Beijing's neighboring province of Hebei also issued an orange alert for rainstorms from Tuesday night to Wednesday night, and initiated a Level III emergency response for flood control. In certain areas, rainfall could reach up to 200 mm and strong winds will occur, the Hebei meteorological observatory warned.

China has a four-tier weather warning system, with red representing the most severe warning, followed by orange, yellow and blue. The national emergency response system also has four tiers, with Level I being the highest.