Today will be a bit of a "transition day" between the two patches of rough weather, WeatherWatch analyst Philip Duncan said.
He said a low in the Tasman Sea was making a beeline for the country, bringing heavy rain to parts of the North Island tomorrow and possibly drenching Auckland with another deluge in the afternoon.
It would also come with a cold southerly from the Antarctic, bringing a drop in temperatures across the country.
"[The cold] will actually affect the whole country. In Auckland, the temperatures are going to drop quite a bit so we're going to go back to winter again ... highs of 15C or 16C on Saturday will drop to 11C on Sunday.
"It's not going to be as long-lasting as the last cold snap, it's not going to be followed by as large frosts across the country but it is going to be cold," Mr Duncan said.
Snow was possible for inland areas throughout the South Island, including Canterbury, coastal Otago and possibly Dunedin, as well as the North Island's east coast and Central Plateau. It would not last long and was looking like a 12- to 24-hour event.
"At the moment these snow snaps, at this time of the year they're not really a problem.
"They bring snow for the ski fields, which is awesome; they bring snow for people who like to see snow and play in it but it doesn't really cause too much of a headache for the farmers," Mr Duncan said.
The low would cross the North Island overnight tomorrow and the weather should clear on Sunday.
MetService said the snow was likely to get down to sea level in Fiordland, Southland, Clutha and Otago during tomorrow morning and afternoon.
Canterbury could be in for snow to near sea level during the afternoon and evening.
Transport could be disrupted, stock in exposed places could be distressed and trees and powerlines could be brought down, MetService warned.
Areas of Auckland received more than half the average rainfall for the month during five hours on Wednesday, causing flooding in parts of the city. Power was cut to more than 1600 homes, the majority in St Heliers, but had been restored to all homes on Wednesday night.
Fire Service spokesman Jaron Phillips said emergency services received 100 calls and went to more than 60 homes and businesses during the peak of the downpour. The flooding was isolated to the Auckland region, he said.
Today's forecast
Whangarei: Morning and evening cloud with afternoon fine spells. High 17C, low 8C.
Auckland: Morning cloud, fine spells. High 15C, low 8C.
Hamilton: Cloudy periods, chance of showers. High 15c, low 4C.
Tauranga: Morning and evening cloud, afternoon fine spells. High 16C, low 7C.
Wellington: Cloudy periods, few morning showers. High 12C, low 8C.
(Source: MetService)