The Environmental Protection Department has warned that the Air Quality Health Index may reach the "Serious" level later today and the index may also remain higher than normal tomorrow.

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

Under the influence of the outer subsiding air of Tropical Cyclone Bailu, Hong Kong is very hot with haze today. 

Higher than normal levels of ozone and particulates have been recorded in the territory since noon. 

Such elevated ozone has triggered the formation of nitrogen dioxide.

Children, the elderly and people with heart or breathing difficulties are advised to reduce outdoor activities.

The Hong Kong Observatory forecasts a southerly airstream will bring showers to the South China coast in the following couple of days. Pollution levels are expected to improve by then.

Click here for the readings.