People with asthma or other breathing problems are encouraged to stay indoors, reports local media.

Worst is the air quality in western Sydney, where the air pollution level is two to three times higher than the national average.

Nearly 50 fires are raging

Nearly 50 fires are still raging in the Australian state of New South Wales, about half of which is out of control. And the weather continues to make the rescue services work more difficult.

- We not only have these high temperatures, 35 degrees and upwards, and the dry air. We also have these changing winds, the rescue services' Shane Fitzsimmons tells ABC News.

About 1,400 firefighters are fighting the fires in the state and, according to Fitzsimmons, may face "real challenges".

Six people have died

After several weeks of severe fires and disaster situations announced last week, Fitzsimmons says it's important not to take anything for granted.

"The last thing we want is for people to be lazy, arrogant or bored when it comes to keeping track of conditions," he tells SBS News.

Six people have been killed and over 500 homes have been destroyed in the fires of New South Wales since the fire season started a few weeks ago. In the last two weeks alone, over 400 homes have been destroyed.

In neighboring Queensland, about 70 fires are ravaged.