Air New Zealand, Qantas, and Virgin have diverted domestic and international flights bound for Sydney because of strong winds and rain.
Other flights were grounded on Thursday until conditions eased.
Torrential rain has caused minor flooding and transport chaos in Sydney and beyond.
The Bureau of Meteorology says about 130 millimetres of rain has fallen at Lucas Heights in the past 24 hours and 110 millimetres in the city.
Some bus services had to be diverted and Sydney's ferries were also disrupted by large swells and strong winds.