The declaration was due to expire before midnight on July 12, but has been extended until at least October 12.
In a statement on Tuesday, Premier Daniel Andrews said he was satisfied COVID-19 continues to pose a "serious risk" to public health throughout the state.
This, he said, justified ongoing public health measures over winter to reduce the risk of transmission and hospitalisation.
NSW Health Minister Brad Hazzard also warned that anyone who isn't fully vaccinated is "crazy" as the state braces for a third wave to peak in late July and early August.
The surge in cases is being driven by two Omicron subvariants, BA.4 and BA.5, and health experts believe the number of cases and deaths will continue to grow.
Meanwhile, state and territory health experts are considering whether to reintroduce mask mandates to curb the case increase.
Dr Chant urged people to consider wearing masks in enclosed spaces to curb the spread of disease in NSW.
As Victoria's death toll rose above 4000, Premier Daniel Andrews said he couldn't make it any clearer that vaccines worked.
However, he stopped short of telling Victorians to don masks outside of the current mandated settings such as health facilities, aged care and public transport.
Prime Minister Anthony Albanese said the Australian Technical Advisory Group on Immunisation was looking at the benefits of widening the eligibility for a second booster.
"We need to make sure that people continue to keep up their vaccinations... making sure that people get their third shot, their booster shot because the numbers weren't as high as the health experts would have liked," Mr Albanese told 6PR in Perth.
On Tuesday there were 3740 people with COVID in hospitals across the country, the highest levels since February during the height of the Omicron wave.
More than 36,000 infections were reported nationally and experts warn case numbers will climb even further as winter progresses.
International arrivals no longer need to declare their vaccination status to enter the country.
LATEST 24-HOUR COVID-19 DATA:
Victoria: 10,056 cases, 23 deaths, 523 in hospital with 29 in ICU
NSW: 13,775 cases, 10 deaths, 1822 in hospital with 64 in ICU
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