Large parts of the North Island will be in the firing line for some bad weather on Sunday with heavy rain and thunderstorms on the way.
MetService said a front will move onto the North Island from the west on Sunday before moving away to the east on Monday morning, bringing a period of rain to many parts of the island.
Parts of the South Island will also see some bad weather with a "slow-moving front" bringing rain to the Westland District, according to MetService.
NIWA said "active weather" is expected over good parts of the North Island on Sunday and Monday.
A graphic put out by NIWA shows central and western parts of the North Island have a medium chance of heavy rain over 25mm and thunderstorms.
The West Coast is also in the firing line with Fiordland expected to see heavier rain and thunderstorms.
The forecasting agency updated its weather warnings and watches on Sunday morning.
An orange heavy rain watch has been issued for the Bay of Plenty about and east of Whakatane, including the eastern ranges from 3pm Sunday until 5am Monday.
MetService warns this area should expect 80-120mm of rain at peak rates of 40mm/h in localised downpours with or without thunderstorms.
An orange heavy rain warning has also been issued for Waikato south of Te Awamutu, inland Bay of Plenty west of Whakatāne, Waitomo, Taumarunui, Taupō, and Tongariro National Park from 12pm Sunday until midnight.
"Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous," MetService said about the areas under an orange heavy rain warning.
MetService has also issued a heavy rain watch for some areas of the North and South Island.
North Taranaki including the Mountain/Taranaki Maunga is under a heavy rain watch from 11am until 9pm on Sunday.
In the South Island, the Westland District south of Franz Josef is also under a heavy rain watch from 9am to 9pm on Sunday.
The forecasting agency said the areas under the watch are expected to see periods of heavy rain that could approach warning criteria, with thunderstorms possible.
On top of the bad weather expected for large parts of the North Island on Sunday, NIWA says the upper half of the island will see the return of humid weather, giving it a "tropical feel".
"Dew point temperatures, a measure of moisture, will increase noticeably this weekend," NIWA said.
"In fact, with air coming from the northwest, much of the upper-half of the North Island will have a tropical feel on Sunday."
MetService short forecast for Sunday:
Northland, Auckland, Coromandel and Bay of Plenty
Cloudy. Patchy light rain, becoming widespread and heavier this afternoon with possible thunderstorms.
Waikato to Manawatū, including Taumarunui, Taupō and Taihape
Rain developing later this morning with heavy falls and possible thunderstorms from Taranaki and Taupo northwards, easing this evening.
Gisborne and Hawke's Bay
Periods of rain developing this afternoon, heavy in Hawke's Bay.
Horowhenua, Kāpiti Coast, Wellington and Wairarapa.
Cloud increasing. Scattered rain this afternoon and evening, but dry about Wellington and southern Wairarapa.
Nelson and Buller
Cloudy periods. Evening showers in Buller.
Marlborough and Canterbury
High cloud. Isolated afternoon and evening showers south of Christchurch.
Westland and Fiordland
Showers, some heavy, with possible thunderstorms and hail.
Otago and Southland
Scattered showers. Thunderstorms and hail possible this afternoon and evening.
Chatham Islands
Cloudy with drizzle at times.
