The heavy rain is expected to begin late Tuesday, when moisture from Typhoon Dolphin to the south meets cold air over northern China.
Some districts in the city are expected to receive more than 200 millimetres of rain in a day. This compares with Beijing's average annual rainfall of 528 millimetres, with most of it falling between June and September.
Dolphin is the most powerful typhoon to hit China this year, according to Reuters. Thousands of flights and hundreds of ferry departures have been cancelled.
In the mountainous Mentougou district in western Beijing, authorities on Tuesday issued the highest level of flood alert, and residents are being urged to stay indoors.
