The Environmental Protection Department has warned that the Air Quality Health Index at some general and roadside air monitoring stations may reach the “Serious” level later today.

The department has recorded a gradual increase in pollution levels since this morning.

It said under the influence of the outer subsiding air of tropical cyclone Danas, the weather in Hong Kong today is hazy with sunny periods and light wind.

Hong Kong is being affected by an air mass with higher background pollutant concentrations, with sunshine enhancing photochemical smog activity and the formation of ozone and fine particulates in the Pearl River Delta region, it added.

The high level of ozone has promoted the formation of nitrogen dioxide, particularly in parts of the urban areas and at the roadside.

The Hong Kong Observatory said a southwesterly airstream will bring a few showers and thunderstorms to the south China coast in the latter part of this week.

It is expected that pollution levels will be improved by then. 

Click here for the readings.