A subtropical low will cross the country today, with the wind shifting from warm northeasterlies to a stiff southwesterly, which will bring cooler, drier weather to the country by Saturday, MetService said.
Auckland and Northland can expect the most blustery weather, with strong wind watches in place.
From 2pm today till the early hours Northland can expect southwest gales that may become severe in exposed places, while Auckland will see southwest gales from 8pm to 6am.
MetService meteorologist Sarah Hadden said there was a complex low system over New Zealand that would pass over the country near Auckland this afternoon.
"Once that moves to the east, we're on the western flank of that low and that's where those strong southwesterlies are."
The whole country would see rain at times today, she said.
"It is quite complex. There are a lot of different features and as they move over areas the wind direction changes bringing bursts of rain.
"Tomorrow the rain is easing so it's an improving trend as that low moves away to the east - it's the warmest, moistest air moving away."
The weather would subsequently become cooler and drier toward the weekend.
By Saturday night the South Island would get lows down to 0C in many areas, with highs of between 6-13C, she said.
Temperatures are set to plunge by up to 10C across the country by Saturday, according to MetService forecasts. Further temperature see-saws are expected in coming weeks - a trend that's typical of spring.
September is expected to be wetter than normal for most regions, with the exception of
Northland, Auckland, Gisborne, Hawkes Bay, Nelson, Marlborough, and Canterbury which should see near-normal rainfall.
Today's weather
Whangārei
Showers to persistent rain in the afternoon. Southwesterlies, strong and gusty from afternoon. High 18C, Low 10C
Auckland
Isolated showers then rain by evening, chance heavy and thundery. Northeast easing, southwest developing from afternoon, becoming strong or gale. High 18C, Low 11C
Hamilton
Possible shower at first then rain developing in the afternoon, heavy and possibly thundery. Light winds, southwesterlies from evening. High 19C, Low 9C
Tauranga
Rain at times, chance heavy and thundery, easing to odd shower by evening. Northerlies dying away in the morning. High 18C, Low 11C
New Plymouth
Rain, more likely from afternoon. Southeasterlies dying out, but gusty southwesterlies developing evening. High 17C, Low 9C
Napier
Occasional rain, easing to for a time this afternoon. Northeasterlies easing. High 18C, Low 10C
Whanganui
Rain, more likely from afternoon. Southerlies, strengthening this afternoon. High 18C, Low 9C
Wellington
Low cloud, showers turning to rain late morning, more persistent and heavier from afternoon. Southerlies, possibly strong by evening. High 13C, Low 8C
Nelson
Occasional rain, persistent and heavier by evening. Light winds. High 16C, Low 9C
Christchurch
Low cloud and the odd shower, turning to rain this afternoon. Southwesterlies, strengthening evening. High 12C, Low 7C
Dunedin
Rain easing to a few showers in the morning. Brisk southwesterlies. High 12C, Low 7C
