A raft of Kiwi towns and cities are ominously poised for official "heatewaves" this week, but meteorologists say high humidity will make most of the North Island unpleasant regardless of peak temperature.
The technical UK criteria to classify heatwaves, which New Zealand also abides by, is that a the daily maximum temperature exceeds the average maximum temperature by five degrees or more for five consecutive days in a given area.
According to MetService, Wanaka is forecast to meet this heatwave label, and a few others get close.
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Auckland won't quite meet the "heatwave" criteria of being five degrees above the January daily max average of 23 degrees, but it's only one degree off on average over the next week.
For the next seven days the daily max temperature will not drop below 27 degrees in Auckland.
And Wellington, with the exception of a few showers on a cooler Friday, will be 25 degrees or above for the entire next week.
However, MetService meteorologist Tom Adams says although daily max temperature definitely plays a role in how hot it feels, the definition of "heatwave" can be misleading to how comfortable you are.
"We're in danger of running into semantics here, the key is it's going to be hot," Mr Adams said.
"The minimum overnight temperature is not going to drop below 20 degrees in Auckland over the next week.
"Comfort levels are a hard one to quantify. When it's very warm you can cool down by sweating but when it's hot and humid that doesn't occur."
Mr Adams said a high pressure system over the country in October and November last year caused less ocean winds off the coast, and that has contributed to warmer sea temperatures.
These humid sea breezes then compound the inland humidity on the North Island.
In contrast frosty winds moving over the alps in the South Island will give some relief to the Canterbury region.
Nelson is one South Island city that is sweltering, with a 30-plus day today, and a seven day forecast in the high 20s.
While in Christchurch the daily max temperatures are in the high 20s to 30-plus degrees over the next week, the daily minimum temperatures are significantly lower than many North Island cities, as they drop to temperatures in the mid-teens.
Gisborne, Masterton, along with Christchurch have all topped 30 degrees today.
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