Beijing has issued a yellow alert for rainstorms, shortly after a heat wave lost its grip on the capital.

Fangshan and Mentougou districts, located in the southwestern suburbs, have raised their own alerts to the highest level of red, after heavy downpours there since Thursday night.

Beijing uses a four-tier color-coded weather warning system, with red representing the most severe weather, followed by orange, yellow and blue.

According to a guideline issued by the Beijing Meteorological Service, under the red alert, traffic authorities should erect warning signs around or dispatch personnel to watch over dangerous sites, such as roads that have flooded or caved in under rain.

Officials with the city's water bureau said they are draining water from submerged roads in urban areas.

Beijing baked under temperatures around 40 degrees Celsius from Saturday to Monday.

The rain is expected to last for three days, said meteorological authorities on Friday morning.

In July 2012, Beijing suffered its worst downpour in six decades, leaving over 70 people dead. Since then, the city government has been reinforcing flood prevention infrastructure and early warning systems to prevent similar tragedies.

Fangshan and Mentougou, among the worst-hit districts during the 2012 storms, "withstood the test last night", said Guo Jinlong, secretary of the Beijing Municipal Committee of the Communist Party of China, addressing a meeting of the municipal government on Friday morning.

Guo contributed the achievement to improved infrastructure and contingency planning.