It's a dreary day for the upper North Island as a surge of warm and humid air covers the sky in clouds.
A NIWA satellite graphic shows how a windy nor'easter flow is circulating over the top of New Zealand.
"The satellite shows how the sub-tropical jet is poking into the tropics and drawing this moisture down to the upper North Island," NIWA said.
"This will keep parts of the upper North Island dreary all weekend."
It means temperatures over the next week will feel more like summer than autumn.
"We're calling it Februapril: over the next week, northerly air flows will bring a good deal of warmth and humidity," NIWA said.
"In other words, it might just feel more like February than April in your region, at times. Cooler air may not move northward until the week of 24 April, at least."
WeatherWatch said the cause is an anti-cyclone to the east of New Zealand coupled with a low in the Tasman Sea and lows in the tropics.
"That creates what we call a squash zone and those north-east winds will become stronger in the days ahead, and as the high gets stronger and moves a little bit further out to our east it will pull down this subtropical airflow and bring it down to New Zealand," WeatherWatch head weather analyst Philip Duncan said.
