MetService is predicting many parts of the country are about to experience a week-long heatwave.
Photo: RNZ / Richard Tindiller
It says many areas will top 30 degrees Celsius in the coming days.
In Central Otago and Queenstown Lakes - which were battered by a chilly southerly change on Wednesday - hot, muggy nights are expected to accompany sweltering days.
A meteorologist, Rob Kerr, said Otago is set for a week of scorching days with many towns expected to be more than five degrees above average.
"There are quite a few towns right across the region, right across much of the country that are going to get close. Places like Kaikoura, Blenheim, Nelson are also going to be pushing the boundary of what might be called a heatwave and it's going to be very warm in general."
NIWA tweeted that the heatwave is expected to build and reach a peak next Friday, with some record or near-record temperatures possible during that time.
MetService is predicting that Christchurch will hit 30C today and 33C on Monday which has prompted the Christchurch City Council to call on residents to conserve water and be fire wise.
The council said works are taking place on the city's wellheads and pump stations, and the less water used by residents, the faster the work can get done.
Fire and Emergency is asking people to clear gutters of leaves and vegetation, and keep grass trimmed to lower the fire risk.
People are also being reminded to be sunsmart and keep hydrated in the hot conditions.
Canterbury's medical officer of health, Alistair Humphrey, said older people, children and those with underlying medical conditions are the most at risk from the effects of heat stress.
Extreme heat can affect blood pressure and hydration, and people should seek help if they feel dizzy, weak or have intense thirst or a headache, Dr Humphrey said.
People should stay out of the sun, avoid extreme physical exertion and ensure babies, children and pets are not left alone in cars, he said.