Hong Kong’s weather forecaster has issued a black rain warning signal as Tropical Storm Podul skirts the city, with residents being warned of flooding and education authorities cancelling classes of all-day schools.

The Hong Kong Observatory raised the signal at 7.50am on Thursday and said it would lower it to red at 11.10am. The No 1 typhoon warning signal, meanwhile, is still in effect.

Red warning signal means that heavy rain has fallen or is expected to fall generally over Hong Kong, exceeding 50mm (2 inches) in an hour.

“There is an exceptionally severe rainstorm in Central and Western districts, and severe rainstorm in Chek Lap Kok of Islands district, Kwai Tsing and Tuen Mun districts. It may cause serious flooding,” the Observatory said, adding hourly rainfall was expected to exceed or had exceeded 100mm.

Flooding swept through the Western district, with some residents spotted knee-deep in water on Connaught Road West.