On Monday, health officials announced the third death in a week, along with 190 new community cases of the virus.
The new crop of cases - including 182 in Auckland - come after 1000 were reported last week, amounting to a seventh of New Zealand's total infections in the pandemic.
The most recent death, of a recent arrival in a quarantine hotel, takes NZ's COVID-19 toll to 32.
The daily highwater mark for cases - 206 - was registered on Saturday, bringing a worrying record hospitalisation count of 81 on Monday.
The outbreak remains centred on Auckland, which will enter a 13th week of lockdown this week.
Despite the roaring case numbers, Aucklanders are set for new freedoms.
Ms Ardern's cabinet will meet on Monday to confirm a decision to increase gathering sizes, and allow retail and public facilities like libraries and museums to reopen from Wednesday.
Top Kiwi COVID-19 modeller Shaun Hendy, a physics professor at the University of Auckland, says the government should reconsider.
"Relaxations are outpacing the vaccination program's ability to bring these case numbers down so it may be a while until we see the peak in this outbreak," he told Radio NZ.
"We're starting to get to the point where we will be putting severe strain on hospital beds and staffing capacity.
"We do need to put the breaks on at this point and have a rethink or we could be facing a much worse scenario."
Hendy said daily case counts of 1000 or more by Christmas were "possible".
"It is certainly consistent with some of the simulations we've done," he said.
Ardern said the government's reopening plans were not contingent on cases dropping, but the government was monitoring for the virus' spread.
"We already know based on all the projections we have that we will see cases rise in Auckland," she said.
"It's not just about cases now that we have a highly vaccinated environment."
As of Monday, 89 per cent of eligible Kiwis are at least partially vaccinated, and 78 per cent are double-dosed with the Pfizer vaccine.
Auckland is at 92 per cent partially vaccinated, and 83 per cent double-dosed.
The holiday season looms large for Kiwis, and many want assurances they will be able to travel around the country free of restrictions.
Under the current rules, the 1.7 million residents of NZ's biggest city are not allowed to leave Auckland without a travel exemption.
Ardern has assured all Kiwis they will be able to spend Christmas with loved ones - but the government is yet to confirm plans on how that will happen.
"We know people want to reunite before Christmas," she told TVNZ.
"Aucklanders must be able to move around beyond the border ... the question then becomes are there some mitigations that we can reasonable put in place to reduce down the risk of (transmission)."
While Auckland remains engulfed in the Delta outbreak - which arrived from NSW back in August - many regions, including Wellington, Tauranga and the South Island, remain without ongoing community transmission.
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