A climate scientist says temperatures in New Zealand could hit record territory this week, as a high mixes with wind and the remains of tropical cyclone Oswald.
Dr Jim Salinger says eastern parts of the North and South Islands could be struck with a heat wave on Wednesday and Thursday that pushes temperatures into the high 30s or even up to 40 degrees Celsius.
Dr Salinger said the temperature has peaked over 40°C only a couple of times in New Zealand.
Canterbury Medical Officer of Health Dr Alistair Humphrey said the elderly are the most vulnerable during heatwaves. He said staying out of the sun and drinking water is key.
GP Council council chair Dr Kate Baddock said heat can reduce blood pressure to extremely low levels.
"If anybody experiences dizziness or lightheadedness or near fainting feelings then they ought to get their blood pressure checked. They may need to have their blood pressure medication modified during this particularly hot spell."
MetService said rain is on the cards for the top of the north and lower south this weekend.