Whangarei and Auckland could expect showers this morning, though the wet weather would clear heading into the afternoon.
The rest of the North Island had a dry, but cloudy outlook. Temperatures would peak in the low 20s in most spots.
The cool weather and rain would continue in the top of the North Island on Thursday and drift south on Friday.
"The top of the North Island and Auckland will see an easterly flow kick in this evening [Tuesday] and overnight.
"Across the country we will see lower temperatures than we have seen over the past couple of days," MetService meteorologist Ravi Kandula said.
On Friday rain would move down through Northland and Auckland to Rotorua, Taupo, Gisborne and other areas in the central North Island.
But the South Island would be settled with no rain expected until Sunday, he said.
Weatherwatch said a dusting of snow in the middle of a New Zealand summer was not uncommon, but it was likely the South Island's summer heat had peaked.
"The next few days will see a gradual warm-up, but long-range data suggests we may not be seeing many 30C-plus days coming up with highs mainly in the mid 20s," a Weatherwatch NZ spokesperson said.
"Overnight lows will be in the single digits for the next couple of nights but by the end of the week and weekend the humid noreast flow around New Zealand will see overnight lows in the mid teens and low 20s."
The North Island would soon be back to high humidity thanks to a subtropical flow. Overnight temperatures would drop only a few degrees from daytime highs.
MetService reports there is moderate confidence rainfall could meet warning criteria in Northland from Friday to Sunday.
Winds could also reach gale-force in Northland on Thursday and Saturday.
Today's forecast
Whangarei: Showers. SE. High 24C Low 18C
Auckland: Showers. E. High 24C Low 15C
Hamilton Scattered showers. E. High 24C Low 13C
Tauranga: Fine. E. High 24C Low 15C
Taupo: Fine. E. High 21C Low 10C
Napier: Drizzle. SE. High 21C Low 16C
Wellington: Fine. High 21C Low 13C
Christchurch: Cloudy. High 20C Low 10C
Dunedin: Cloudy. W. High 18 Low 12C