"Highs can bring plenty of dry weather, but they can also bring plenty of cloud to certain areas - either way, the day won't be stormy at least."
Mr Duncan said that with the high located east of the country it would mean a gentle but slightly cloudier easterly flow over the upper North Island and this may produce just a couple of light isolated showers and bring in a little more cloud.
"We see a few isolated showers mainly in rural areas - nothing that should ruin the day for most but perhaps more of a little annoyance for some.
"Auckland might have a shower - but the day is still a mostly dry day," Mr Duncan said.
"Highest risk areas for any showers will be the West Coast, the North Island Central Plateau and perhaps very northern New Zealand, mostly north of Auckland - but again it shouldn't be much."
WeatherWatch said the hottest and sunniest weather looked to be the eastern side of the South Island where highs may reach closer to 30C inland.
Nearer to the coast a cooler breeze may shave several degrees off the heat - but still leaving a warm to hot day.
How the weather is shaping up
Upper North Island:
Fairly Cloudy, light nor'easters. Low risk of a shower, the risk mainly in eastern Northland and perhaps some parts of the Auckland region. Dry for 90 per cent of these areas at this stage.
Highs: Not overly hot, early 20s for most. Mid-20s more likely well inland where it may be sunnier further south.
Lower North Island:
Sunny and cloudy spells with afternoon cloud build ups near the ranges, especially the central North Island volcanic plateau south towards the ranges of Manawatu, where a late downpour is possible. Hot inland.
Highs: Low to Mid 20s.
South Island:
A warm north to north west flow will mean Fairly cloudy on the West Coast - may be a shower there too, especially southern Westland - otherwise dry. Dry and hot elsewhere, especially inland and towards the east, with nor'westers developing it may get closer to 30C for some areas such as inland Canterbury. Risk of a late isolated shower in the Southland region too, but will be warm.
Highs: 19C to 30C - hottest inland to the east.