There will be no let up from the heat today as temperatures soar around the country.
NIWA forecaster Chris Brandolino told The AM Show Auckland Anniversary Monday is going to be "real hot", with some regions reaching up to 40degC.
The heat will be at it's most extreme over the South Island, with temperatures peaking on Tuesday.
While the North Island won't get such extreme temperatures, the humidity will increase the feel of the heat.
Mr Brandolino says the heat is set to continue throughout the week, with humid, stormy weather making it's way to New Zealand on Thursday.
This is the result of a tropical cyclone brewing in the Coral Sea.
The humidity is expected to last two days as it attaches itself to a low front moving across the country before a southerly comes through to clear it up briefly.
But WeatherWatch says there is a possibility of a "double dose of tropical trouble".
A second storm may be brewing which could impact New Zealand around Waitangi Day, although it is too far out to confirm it will hit the country.
The tropical storm could spell heavy rain for both islands alongside the heavy heat and humidity if the low tracks south.
At this stage, neither low is forecast to hit New Zealand as a storm.
January 2018 is tracking to be New Zealand's warmest month on record since 1909, with an average temperature of at least 19.85degC.