'Great Cool Down' to smash heat wave, temperatures to dramatically plummet on Friday

Prepare New Zealanders; the "Great Cool Down" is coming to some areas on Friday and Saturday with temperatures expected to dramatically drop after a week of hot weather.

Kiwis have been sweltering in scorching temperatures, frequently crossing the 30degC mark and shattering records in areas like Richmond and Kelburn in Wellington.

On Thursday the peak of the heat wave looks like it will strike, with NIWA forecasting North Canterbury to hit 37degC and Wairarapa to reach 34degC.

But the hot weather is predicted to end for some regions as WeatherWatch warns of the "Great Cool Down".

South Islanders may want to shelve the fan, especially in Central Otago which could see temperatures start to fall on Friday.

"It may not be a clear cut change, others may notice Friday ends cooler and Saturday is overall cooler," said WeatherWatch.

In Central Otago, temperatures are forecast to drop by as much as 14degC compared to the mid-twenties expected on Thursday. Nelson, Marlborough, and Canterbury can expect a drop of roughly 12degC over the period, according to WeatherWatch.

Those in the North Island will also get some reprieve from the warmth, but it won't be as dramatic as in the south.

The most noticeable change will be in the Hawkes Bay which is set to shift away from the highs of 37degC it saw on Monday to about 19degC in some coastal areas on Saturday.

Further north, the cooler change may be felt, but WeatherWatch says it "depends how sensitive you are".

"The temperatures won't be dropping much but the humidity may drop a little for a day or so."

MetService forecast temperatures in the South Island should begin to drop on Friday, but the coolest weather won't be felt until Saturday.

While many Kiwis will be glad to see the back of the heat wave, warm temperatures are expected again on Monday and Tuesday.

The record weather is prompting warnings about safety, after a spate of instances of children being left in hot cars.

Napier woman Chrystal Alatasi found two upset children inside a hot car at a Napier supermarket on Sunday, when the temperature reached 33degC.

"I couldn't believe the amount of heat that came out of that vehicle... it was like opening an oven," she told The Project.

There have been three separate incidents of children being found stuck inside hot cars during this week's heat wave.