Beijing's municipal government advised employers, middle schools and elementary schools to be flexible in their scheduling when confronted with extreme weather, such as heavy rainstorms, according to a new emergency response plan released on Wednesday.

The city said that when a red alert is issued - the most serious warning in the city's emergency response plan for flooding or landslides - municipal departments must make their best efforts to protect residents.

Meanwhile all kindergartens, primary schools and middle schools should be closed, and companies should change their working schedules, it said.

When an orange alert - the second-highest level - is issued, all institutions can adjust time schedules to relieve rush hour traffic pressure.

The municipal weather authority will issue one of four alarms based on the scale of the rainfall, traffic conditions or other factors under the new rainstorm warning system. Prewarning forecasts will be sent directly to cellphones.

Several serious downpours have deluged the capital since the flooding season began in June, keeping the city's contingency forces on alert.

On Wednesday afternoon, a sudden storm with heavy rain and hail hit the city's northwestern areas, submerging 18 vehicles parked on a low road. No casualties were reported.

The average rainfall was around 19 mm, in alignment with a blue alert, the lowest level.

The northwestern districts and suburbs witnessed the most rain. The heaviest rainfall measured around 50 mm per hour in Haidian district.

The district's government said one area at Tiancun East Road flooded when tree branches blocked drainage holes, making the water rise quickly to around 1.5 meters and inundating 18 parked cars.

Insurance companies have started investigations for future claims.

Hail hit Changping district around 6 pm, and many residents posted pictures of the hailstones online, showing some as large as table tennis balls.

Around 400 hectares of farmland was hit by the rainstorm, with economic losses estimated at around 5 million yuan ($806,000), the municipal flood control office said.

The capital has made efforts to increase its flood control ability to avoid deaths ever since a wild storm raked Beijing on July 21, 2012, killing 79 residents.

Major roads in downtown areas that are prone to flooding have been improved with more powerful pumps, aiming to drain water quickly.

Hailstorm pounds suburban Beijing	Beijing rainstorm cancels flights, kills airport worker