The eight cases in the 24 hours to 8pm on Monday came from a record of almost 44,500 tests, Premier Gladys Berejiklian said on Tuesday.
Seven of the eight cases were linked to the northern beaches cluster, and another was uncovered in a nurse transporting patients in hotel quarantine.
A decision will be made on gatherings for Christmas day when the NSW government cabinet meets on Wednesday.
"We'll be looking to make a decision tomorrow based on what we know and understand during the day ... on what the future of the situation on the northern beaches, greater Sydney, will be," Ms Berejiklian told reporters.
Chief Health Officer Kerry Chant said testing rates had lifted across all of greater Sydney with a massive surge on the northern beaches.
The so-called Avalon cluster now totals 90 infections.
New alerts were on Tuesday issued for Sydney venues visited by people infected with Covid-19, mostly on the northern beaches.
These add to the alerts posted on Monday night for cinemas, restaurants, hotels, cafes and gyms at Mona Vale, Newport, Narrabeen and Warriewood, as well as the Avalon Beach RSL Club - all on the northern beaches.
There were also alerts for Cortex Gym at Alexandria, the London Hotel at Paddington and the Paragon Hotel in Sydney's CBD.
NSW had recorded 15 new locally-acquired cases on Monday, which was half of the 30 locally-acquired cases recorded on Sunday.
Deputy Premier John Barilaro earlier on Tuesday rejected widespread calls to mandate mask-wearing in public, saying it wasn't "the be-all and end-all".
"More people are wearing face masks in public spaces than I have seen ... there is no need to make it mandatory," he told Nine's Today show on Tuesday.
But Opposition leader Jodi McKay said the government needed to act on mask-wearing because people were out shopping and at religious gatherings.
Dr Chant has said any decision on further restrictions would be based on the prevalence of Covid-19 outside the northern beaches.
So far, five Covid-19 cases have been linked to Turramurra Salon for Hair and two cases to the Rose of Australia hotel in Erskineville.
Every state and territory has now blocked Greater Sydney residents from entering and some have also blocked people living on the Central Coast and in the Illawarra-Shoalhaven regions.
NSW has from Tuesday begun forcing international aircrew personnel into police-supervised hotel quarantine arrangements.
Meanwhile, Australia said two people who travelled from Britain to New South Wales state were carrying the mutated virus. It axed dozens of domestic flights while New South Wales locked down more than 250,000 people.
Some scientists said the prevalence discovered in Britain might be down to more thorough detection.
"I think we will find in the coming days that a lot of other countries will find it," Marc Van Ranst, a virologist from the Rega Institute for Medical Research in Belgium, told broadcaster VRT.
For more information go to: health.nsw.gov.au
