Sunday would bring a few showers about the coast but plenty of sunny breaks.
Despite the sunshine, Mr Law said there would be "chilly starts" during the next few days, with a chance of frost in rural areas.
The possibility of frost was heightened by an absence of cloud cover and strong winds.
Air temperature lows of 3C could be deceiving today and tomorrow, with the ground temperature likely to dip below freezing. The overnight low would drop to a frigid 1C on Sunday.
Mr Law said a westerly flow would return to the region next week, which meant dry weather due to rain protection from the ranges in the east.
But rain might creep temporarily past those defences on Tuesday.
WeatherWatch.co.nz forecaster Aaron Wilkinson said western parts of the North Island would bear the brunt of showers next week, while the east coast enjoyed sunny weather.
Mr Wilkinson predicted "some really nice warm days", with 18C midweek.
"You'll start to notice it warming up from Tuesday."