New Zealand will stay in the orange traffic light setting ahead of the Omicron winter spike, the government has announced.

The country has been at the orange alert level since 11.59pm at 13 April.

In a statement, Covid-19 Response Minister Chris Hipkins said the next review would be in late June but for now, the Orange setting remained appropriate.

"While daily cases numbers have flattened nationally, they are again beginning to increase in the Northern region and hospitalisation rates have also increased slightly over the past month," he said.

He said modelling showed there was also likely to be a second wave appearing, and warned that while case numbers for now remained fairly steady the arrival of new strains of cold and flu as winter was nearing were adding to the workloads of already busy hospitals.

"I urge everyone to continue to be cautious and think about the health of others, especially those who are immunocompromised or at higher risk of long-term health impacts from infection. Please also get boosted, if you haven't already."

He said public health measures like isolation, vaccination and mask wearing continued to be the main defences against Covid-19 and masks would continue to be required in many indoor settings.

At Orange, masks are required on flights, ferries and passenger terminals, public transport and taxis, in retail settings including supermarkets, public venues, healthcare and vet clinics, courts and tribunals, and government-run buildings.

Masks are otherwise encouraged indoors, although they may be removed at eating and drinking venues. Businesses may also require them as a condition of entry.