Kiwis are sweating and Tuesday night isn't expected to be any better - nor is the rest of the week.
Overnight temperatures are above average in many North Island centres and forecasters predict a "warm and muggy" rest of the week.
Auckland, for example, will only drop to 19C overnight before climbing back to 27C on Wednesday.
And it's not just North Islanders sweating - Christchurch Airport recorded 33.6C on Monday and 27C on Tuesday, with 26C expected on Wednesday.
"A lot of places in the South Island that aren't used to this humid weather will certainly be feeling it," MetService meteorologist Kyle Lee said.
The forecaster says the humidity is being caused by a "lingering front" lying over the central North Island.
"New Zealanders have been inundated with hot and muggy air to start the working week," MetService said on Facebook.
"Humid conditions are set to continue for much of the week with overnight temperatures not expected to drop below 15C for the North Island main centres tonight [Tuesday]."
Click here for our tips on how to stay cool during the heat.