COVID-19: What NZ's alert level 4 lockdown announcement means for Auckland and Northland

From next week, most of the country will shift down COVID-19 alert levels - but Auckland and Northland will stay under at our strictest lockdown level for a while yet, it's been announced.

Prime Minister Jacinda Ardern on Friday afternoon revealed all of New Zealand south of Auckland will move to alert level 3 at 11:59pm on Tuesday.

But while for most Kiwis the prospect of takeaways and a nice frothy flat white aren't far away, Aucklanders and Northlanders will remain at alert level 4 well into next month.

The length of that further period spent in strict lockdown has not been set in stone yet, and will be discussed by Cabinet on Monday.

However Ardern warned that for Auckland, it's likely to be for another fortnight from next Tuesday. That means the region's 1.7 million people could be at level 4 until mid-September, or even beyond should lockdown be extended again.

Director-General of Health Dr Ashley Bloomfield has some positive news for Aucklanders, though, confirming days of zero cases are not necessary there for a shift down alert levels.

He says it's more about the type of cases than the quantity; health officials are keeping a particular eye out for "unexpected" cases, rather than those already in isolation or unlikely to pose a risk to the community.

Ardern is calling on Aucklanders to do the "heavy lifting" in suppressing the Delta outbreak, saying it's incredibly important they stick to the rules as Delta infecting one family member means it's likely their household contacts will get it too.

Auckland is by far the biggest hotspot in this latest New Zealand COVID-19 outbreak, with 333 community cases, so it's clear why having stricter public health measures there is a priority for the Government.

As for the rationale behind keeping COVID-free Northland at alert level 4?

Ardern says that's due to the positive case in Warkworth - a town in the Auckland region but close to the Northland border - and the need for further contact tracing.

She says she doesn't believe the region will be under a strict lockdown for as long as Auckland.

No decisions have been made about how long most of New Zealand will be at alert level 3, but Ardern says there will be weekly reviews of alert level settings starting September 6.

She wouldn't say if it was possible Auckland may be at level 4 while the rest of the country was at level 2.

Having parts of the country at one level and parts at another means a border will be established at Bombay, just south of Auckland, to prevent people moving between regions unless they have an exemption.

Travel between Auckland and Northland is not allowed despite the matching alert levels, as it's not allowed at either level 3 nor 4.