Weather forecast: Surf's up as big chill creates giant swells

It was the perfect storm for surfers over the weekend as waves slammed coasts around the country.

The Antarctic blast sent surfers to Otago as monster swells combined with perfect conditions to create giant barrels peeling off a series of outer reefs along the southeast coastline.

The waves are rare, requiring a swell of at least 8m combined with the right wind speed, swell angle and tide.

Local photographer Derek Morrison said each surfer was towed into the wave before attempting to ride in and out of the giant barrels.

"They're without doubt waves of consequence and it is a hostile environment with a swell like that, so you need all hands on deck in case something goes awry," said Morrison, who runs the surf photo blog Box of Light.

The waves were part of a complex weather system which also pulled chilly air up from the Antarctic and across the country, making Sunday night the coldest night of the year for most areas.

But the weekend's wintry temperatures have since made way for more autumnal weather patterns.

Frosts were still expected overnight in parts of the North Island as the skies remained clear, with inland areas dipping below 0°C. Taumarunui temperatures were approaching -2°C at 11pm.

That was expected to be colder than most of the South Island, where a blanket of cloud kept in some of the heat. At 11pm it was still a balmy 10°C in Invercargill.

Normal autumn weather patterns are forecast for the last week of autumn - although it would be wise to keep the winter woollies ready. A pattern of highs and lows will bring changeable weather with some rain as winter approaches.

A series of ridges and troughs will bring sunshine and intermittent rain for the rest of the week, along with warmer temperatures, according to MetService.

A period of rain is expected in the west of both islands, with a drier run expected in the east, according to MetService. Rain was likely to hit the North Island by midnight Monday.

"With this typical autumn weather pattern, the South Island's western coasts are expected to bear the brunt of the rain" MetService meteorologist April Clark said.

The east in particular would only receive a "weakened blow" from the front, with plenty of sun in between.

Your weather

WHANGAREI Partly cloudy, light winds. H 17C, L 11C

AUCKLAND Fine, cloud increasing with light winds. H 16C, L 11C

HAMILTON Cloud, few showers, northerly breezes. H 14C, L 7C

TAURANGA Fine at first, some afternoon cloud. Light winds. H 15C, L 9C

WELLINGTON Mainly fine, cloud in north. Strong northerlies. H 15C, L 9C

CHRISTCHURCH Fine at first with frosts, northerlies dying out. H 16C, L 5C