The air quality in Sydney has dropped to "hazardous" levels through smoke and fog as Australia prepares to prevent catastrophic bush fires during its summer months.
Australian authorities urged older people, children, and anyone with heart or lung disease to avoid exercising outdoors and stay inside as much as possible, the Australian Associated Press reported.
Weather experts said the smog is lingering over Australia's biggest city due to a lack of wind.
The haze is being caused by rural fire brigades in New South Wales deliberately setting sections of the countryside on fire to halt the spread of out of control bushfires.
Australia experiences hundreds of wildfires each year with some of them raging into deadly infernos that threaten towns and kills scores of wildlife.
The deliberate fires have been halted to allow the lingering smoke to pass.