COVID-19 cases have begun to stabilise but Premier Gladys Berejiklian warns she "won't hesitate to make difficult decisions if she has to" unless case numbers start dropping.
NSW recorded 65 cases to 8pm on Wednesday evening in what Premier Gladys Berejiklian described as a "welcome drop"
"But it comes with a warning," she said.
"Based on the fact we had 28 people in the community while infectious, I expect that we will have higher case numbers tomorrow.
"Even though the case numbers were lower, 28 is too high."
Ms Berejiklian said there had been a "stabilisation" but it was vital the figures started falling, which she said could only be achieved with fewer cases mobile while infectious.
"My strongest message to everybody is keep doing what you are doing, keep sticking to the rules," she said.
"Regrettably a number of people who were infectious in the community is because they went to pharmacists to get medical attention, they went to GPs.
"It's so important that if you have symptoms, the only place you should be going ... is to get tested and home to be isolated."
More than 58,000 tests were conducted across the state in the 24-hour period.
"I just really want to thank the community for responding to our calls for testing," Ms Berejiklian said.
Lockdown was extended for Sydney, the Central Coast, Blue Mountains and the Illawarra on Wednesday, with Ms Berejiklian confirming the rules will not be lifted before July 30.
Earlier, Queensland extended mandatory mask rules for a further week across 11 local government areas including Brisbane, Noosa and the Gold Coast.
The northern state recorded three new cases of COVID-19 in the figures announced on Thursday.
The cases include a 12-year-old who returned from the US with his mother, the child's father who collected the pair from the airport and a fully Pfizer-vaccinated Brisbane International Airport worker aged in her 40s.
The airport worker was symptomatic but "not critically sick", and worked three shifts while infectious.
The youth became unwell after returning to Queensland from completing hotel quarantine but health authorities said the case was contracted during his time in Sydney.
"It's unlikely to be a long incubation but that's not impossible," Queensland chief health officer Dr Jeanette Young said.
Queensland Premier Annastacia Palaszczuk said the prolonged mask measure was designed to prevent lockdown in her state.
She also urged Queenslanders not to travel into NSW or Victoria as "spot fires" continue to boost case numbers in both jurisdictions.
"What we're seeing is these outbreaks happening across the country," she said.
Dr Young said the southeast Queensland conditions would give authorities a chance to prevent the spread.
"We now have to see where they've been working and who they've come into contact with," chief health officer Jeanette Young said.
"People should re-consider any need to go to NSW because they could have an outbreak anywhere.
"Similarly in Victoria ... they've got multiple outbreaks due to multiple incursions of the virus from Sydney.
"If you're already down there, I think you need to look at your risks to stay there."
Police described the State of Origin crowd's behaviour as "excellent".