It will feel like a summer's day in some centres around the North island - once the fog that has blanketed much of the region lifts.
Napier looks set to beat its previous record high for May with a temperature of 27C this afternoon and neighbouring Hastings is expected to reach 26C.
Whangarei and Gisborne could be hotter than usual too, at 24C and Auckland is expected to reach 22C.
But this morning, in the country's biggest city, humid air brought a considerable amount of fog. It caused traffic disruptions and delays to ferry services.
Auckland Transport tweeted that Birkenhead and Northcote Point ferry passengers may face delays because of fog on the western side of the Harbour Bridge.
West harbour passengers were also due to face delays.
There was also fog around the central and upper North island.
But it wasn't enough to affect flights coming in or out of Auckland and Hamilton airports.
MetService meteorologist Tom Adams expected the air would be clear by mid-morning.
He said for the most part the weather was staying true to the stereotypes. "Wet on the West Coast, windy in Wellington, dry in the east and warm in the north," he said. "It's the meteorological equivalent of sticking to what you are good at."
But he said this didn't rule out a few surprises in the mix, with wind and rain reaching warning levels at times.
"Rainfall warnings are currently issued for parts of the West Coast and the severe weather outlook has a chance on Thursday of heavy rain for Kapiti and gales through Cook Strait."
He said it was worth keeping an eye on the forecast. "It is not unusual for autumn weather to get pretty wild."
It was largely fine weather in the main centres today.
Wellington was expected to be cloudy, with the chance of scattered showers though there'd be a strong northwesterly winds gusting up to 90 km/h. Today's high in the capital was forecast to be 18C.
The warm temperatures in Hawkes Bay are expected to continue tomorrow with another 26C high, and a fine day with variable high cloud and northerlies picking up.
WeatherWatch head weather analyst Philip Duncan said warm spells in autumn were normal, but not as warm or as long as this one - which is believed to potentially extend into the third week of May.
Federated Farmers Hawke's Bay provincial president Will Foley said normally high temperatures in May meant more grass growth, but because the weather had been very dry the expected heat would just "compound the problem".
Farmers had enjoyed a good spring, he said, so they would have some feed on hand, but others would be holding off getting more stock until there had been enough rain.
"Most farmers thought that with the El Nino predictions that they had dodged a bullet."
He said unfortunately farmers would not be getting away without a dry spell.
"Farmers are gutted," he said. "We had such a good season up until the start of the year and now the weather has come back to bite us."
Hawke's Bay Fruitgrowers Association president Lesley Wilson said most fruits were off, so the high temperatures would not affect fruit quality.
Growers would be keeping an eye on irrigation to make sure trees were well watered going into winter.
Today's top temperatures:
• Napier 27
• Hastings 26
• Whangarei 24
• Gisborne 24
• Blenheim 23
• Kaitaia 23
• Kerikeri 23
Other main centres:
• Auckland 22
• Tauranga 22
• Hamilton 22
• Thames 22
• Christchurch 21
• Nelson 20
• Rotorua 19
• Dunedin 19
• Queenstown 18
• Wellington 18
- Hawkes Bay Today and NZ herald staff