A severe thunderstorm warning has been issued for parts of Sydney's north, with residents warned to brace for heavy rainfall and hail stones.
The Bureau of Meteorology on Friday morning said the storm was moving in an easterly direction from Hornsby towards the coast.
It would hit the northern beaches area after 9am.
Thunderstorms are likely to produce large hail stones, heavy rainfall and strong winds, and could stretch as far north as Wyong.
The weather system could also affect the Blue Mountains area.
The warning comes after a thick layer of dust settled upon houses and vehicles around Sydney on Friday morning due to a western NSW dust storm.
Air quality in eastern, northwest and southwest Sydney on Friday morning is at hazardous levels, as well as in the Illawarra and Central Tablelands.
Australian Associated Press