The east would remain relatively fine, sheltered by the Southern Alps, but may get gusty northwesterly winds.
Further north, temperatures would remain relatively more balmy.
Auckland, Hamilton and Tauranga would hover around 18 or 19C while Dargaville and Whangarei were forecast to have a high of 20C.
While the North Island would have relatively warmer weather, most spots would also see a smattering of rain.
The lower North Island would experience some wet Sunday weather - mainly kicking in this afternoon.
Showers would develop into heavier rain in Auckland and Northland from the morning, with heavier rain due later today.
The East Coast would be spared from the wet weather, with the Hawke's Bay looking set to stay dry for the rest of the weekend.
The rain was short-lived for most of the North Island, and would clear in most spots to make way for a fine start to the week.
Temperatures would sit around 19C for the upper North Island and around 17C further down the island.
In contrast, South Islanders might want to keep the brollies handy - especially those further down the island.
Greymouth and Invercargill would see consistent rain up until Wednesday, while Queenstown was forecast to have showers for most of the week.