Emergency departments in the North Island are at capacity and struggling under a higher-than-usual intake of patients.
The Waikato District Health Board (DHB) has advised non-urgent patients to go to a GP or an after-hours medical centre.
Chief executive Nigel Murray said it was usually a quiet time of year for the emergency department, but this year had been an exception.
"Particularly our hospital's emergency department is extremely busy, much more than the usual influx of patients at this time of year. It's a very busy time, our doctors and nurses are working really hard to ensure that patients are tended for and cared for in a timely manner."
He said non-urgent patients could also use an online service to consult a doctor.
In Auckland, a DHB spokesperson said its emergency departments were also above capacity.
She said the after-hours centres often put on a surcharge for public holidays, which drove patients to the hospitals.