The front will bring heavy rain to the west of the South Island from Monday, and odd falls in the east, Metservice forecaster Cameron Coutts said. As the week progresses, showers and winds are picking up around much of the country, and current balmy temperatures will drop down to below average in some areas.
While the east of both islands can expect temperatures in the 20s over the next couple of days, as the front moves through these will drop back down to the mid teens, Coutts said.
"The whole country sort of gets into a cooler sort of southwesterly flow.
"The odd place will be a few degrees below average for this time of year."
Snow is also expected in parts of the South Island and may affect roads in high areas.
The showery weather may not reach some sheltered areas but is expected to hang around until at least Thursday, meaning Kiwis should lap up today's sun while they still can.
Aucklanders can expect mostly fine weather with some cloud today and a high of 16C while Hamilton is slightly warmer on 17C.
Whangārei, Tauranga and Rotorua will be baking in sunshine with 18C.
Met Service Sunday forecast: For all the North Island Fine, apart from areas of morning and evening cloud. Nelson, Marlborough, Buller, Canterbury, Otago, and Southland Fine, apart from areas of cloud or fog morning and night. Westland Mostly cloudy. Showers developing in the south this evening. Fiordland Cloudy, with patchy drizzle in the west, turning to rain tonight Chatham Islands Mostly cloudy