Nurses will be walking off their jobs nationwide for 24 hours from 7am after rejecting the latest pay offer.
The more than 30,000 New Zealand Nurses' Organisation members joining the strike leaves the country's health system without 70 per cent of its frontline workforce - the biggest strike to hit the sector in 30 years.
NZNO industrial services manager Cee Payne said life-preserving services and contingency plans would be in place across the 20 district health boards.
"Patient safety and public safety is paramount," Payne said.
The rallies for Auckland, Christchurch and Wellington would begin at 7am outside the main hospitals.
At Auckland hospitals, nurses would be greeting those coming off the night shifts supporting Life Preserving Services Responders before joining a march down Queen St at 11am.
Up to 8000 people have had procedures rescheduled ahead of today's nurses strike and hospitals have been ramping up preparations to make sure they could treat those who are in urgent need.
Capital and Coast chief medical officer John Tait, speaking on behalf of health boards around the country, said between 6000 and 8000 elective procedures would be deferred.
Acting Prime Minister Winston Peters said the Government was very disappointed that nurses had voted to reject the latest pay offer.
"We offered $500 million," Peters said.
"That is a massive increase on what they were offered when we became the Government. We've doubled it and found 500 new nursing places and new career steps for them to move more quickly up the scale. That's the best we're able to do. We're not kidding when we say that."
The Government encouraged DHBs and NZNO to continue with urgent facilitation talks over the next two days, Peters said.
"We need the public to be prepared. We've made all the steps possible we can to ensure there is the least amount of sacrifice, or medical difficulty, with respect to potential patients," Peters said.
Anyone with an urgent medical need should not hesitate to dial 111 or go to an emergency department.
For day-to-day medical queries the public can contact their GPs or use the 0800 Healthline number.
People with appointments or surgeries that have been postponed should have been contacted by their district health board.
If you have something scheduled and have not heard otherwise you should attend as usual. If you are unsure, contact your health board.
Patients in hospital will have to wait longer for help with those things. In some cases, whanau, volunteers and doctors will be asked to help out.
Patients deemed not to require "life-saving" care, who require assistance with tasks such as turning on bedrests, inserting intravenous pumps, help going to the bathroom and bathing will wait longer. Family, volunteers and doctors have been asked to help out in some cases.
Some services like Family Planning are not affected by the strike, but others could be if the nurses are paid by the DHB. If you already have an appointment booked, check it's still on.
For the full list of strike activities please go to the Health Needs Nursing Facebook page.