The lockdown was originally set to end on Saturday, August 28.
It comes as the state recorded 1029 new locally acquired COVID-19 cases overnight and three deaths, a 30-year-old man, a 60-year-old man and an 80-year-old man, all who were not vaccinated.
Deputy Premier John Barilaro said regional NSW was “on a knife’s edge”.
“We’ve got areas of concern like Western NSW, the Far West, we still have cases in Illawarra and the Hunter, New England area and the Central Coast,” he said.
“Sewerage surveillance is showing fragments in parts of regional and rural NSW where we have no known cases.
“The decision to extend the lockdown is one to protect communities and protect the regions; It’s a tinder box ready to explode.
“I do apologise to those communities that don’t have cases today, but the reason you may not have cases is because of the restrictions in place.”
After reaching six million COVID-19 vaccinations earlier in the week, Ms Berejiklian announced some allowances in the coming weeks for fully vaccinated adults.
“From September 13, in the local government areas of concern, a household will be able to go out for an hour of recreation, on top of the hour of exercise – so a family will be allowed to sit in a park, so long as the adults are vaccinated,” she said.
“In relation to areas outside the LGAs of concern, the rest of Sydney and NSW, five people will be allowed to gather outdoors so long as all adults are vaccinated.
“It means if you have friends or relatives within your LGA or within the five-kilometre radius, you will be able to congregate together in an outdoor gathering of five, rather than just two from your household.”
Ms Berejiklian also flagged easing of restrictions when 70 per cent of the eligible population is fully vaccinated against COVID-19, which she said is expected to arrive in October.
If we continue to sprint towards vaccination we expect that 70 per cent double dose figure to arrive sometime in October.
“NSW is calling on industry and citizens to be ready for when we reach 70 per cent fully vaccinated,” she said.
“That’s when things will start to open.
“The NSW Government will start conversations with industry but we do say that the condition of you participating in the reopening will be being vaccinated, because when you start opening at 70 per cent, there are some activities only vaccinated people can do.”