Thunderstorms bringing heavy downpours, hail and a small chance of a tornado in Auckland could be arriving within the hour.
The first band of isolated thunderstorms is moving into western Waikato and Auckland region from the Tasman Sea.
MetService meteorologist Tom Adams said the thunderstorms would bring heavy downpours to some areas, but won't be felt in other areas.
"It's a very bubbly convection system," he said.
WeatherWatch analyst Philip Duncan said the thunderstorms would be noticed around Auckland and Hamilton between 9.30am and 11am.
MetService said the first band of thunderstorms will pass over, leaving cool air and some strong wind gusts. Hail could also fall in parts of Auckland.
"There is a small chance of a tornado, but it's not a Kansas tornado," Mr Adams said.
"But we do have it in our warnings, there are small effects with the thunderstorms that are hard to distinguish from," he said.
The rain would be short bursts of heavy rain, Mr Adams said.
"It won't be as bad as yesterday."
Once this morning's band of thunderstorms moves away, several more will follow, with growing intensity, Mr Adams said.
From evening the rain falls become more frequent and heavy for the top half of the North Island.
Temperatures are warm in Auckland currently, but will drop a degree or two when south-westerly winds arrive.
In Wellington it's fairly warm this morning on a day where showers are expected to hang around.
For the South Island, there's scattered rain that will become more frequent as a southerly wind arrives.