Soaring temperatures in Hawke's Bay are putting pressure on the region's emergency departments.
Hawke's Bay DHB chief medical officer Dr Mark Peterson says medical services have responded to several cases where elderly patients have overheated and fainted.
Infants, the sick and elderly are most at risk.
"We have seen a number of people presenting both to their GP and to the emergency department with dizziness, fainting type symptoms, and some have obviously actually fainted."
Dr Peterson is encouraging patients to stay hydrated to avoid heat-related illness.
"If they're feeling unwell, then the first one to call should always be their GP, or one of the accident and medical centres that are open during this junior doctors' strike."
Junior doctors began a second lot of strike action on Tuesday and it ends on Friday morning.
"We felt we've all got to the point where we won't make any more progress in our negotiations if we don't strike," Auckland Hospital junior doctor Kathryn Foster told Newshub on Tuesday.
"It never feels good to walk out of an employment situation, we want to be there for our patients, we want to be working, but, we feel we have no choice."
Dr Peterson says many centres have extended their opening hours to accommodate the demand.
Temperatures on Thursday are forecast to peak in the high 20s.