The Environmental Protection Department warned that the Air Quality Health Index may reach the “Serious” level later today.

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

It said the city is being affected by an air mass with higher background pollutant concentrations and that a high level of ozone has promoted the formation of nitrogen dioxide.

Children, the elderly and people with heart or respiratory illnesses should reduce outdoor activities.

The Hong Kong Observatory forecasts that the weather will be generally fine and very hot today and tomorrow.

Pollution levels are expected to remain higher than normal until the wind strengthens next week.

Click here for the readings.