Weather: Severe frosts and heavy snow forecast

Areas of the lower South Island are expected to get heavy snow. Photo / File

Icy temperatures and severe frosts will replace the heavy rain that caused flooding chaos over the weekend, making for a shivering cold start to the week.

The country has been hammered over the last week by a winter storm which brought heavy rain to many parts of the country and heavy snow to parts of Canterbury and North Otago.

Temperatures plummeted in the south but stayed mild in the north, with Napier and Gisborne both approaching temperatures of 20C.

Flood-afflicted North Island residents can expect some good news this week, with the downpour-dumping weather system having moved away to the east of the country, meaning the rain will ease.

But MetService meteorologist Emma Blades warned the system would be replaced by a cold southerly flow.

"Temperatures will drop across the whole country over the next couple of days with severe frosts forecast for sheltered places," Ms Blades said.

"Add the wind chill factor from strong winds in the east and it's going to start to feel bitterly cold for some."

Ms Blades said temperatures in Timaru could drop to around -9C at night next week, which was very cold compared with the town's average minimum temperature of 0C for this time of year.

Ms Blades said a watch was issued this morning for heavy snow in southern Fiordland, Southland, and southern parts of Otago, including Clutha and Dunedin.

"That is for snow to accumulate above 200m from this evening until Monday morning."

Areas around the Canterbury Plains north of Ashburton were likely to get snow near to sea level, she said.

"That could be heavy especially at the Port Hills and Banks Peninsula."

Howeverm Ms Blades said the snow would not be as significant as in recent days.

"It's a different kind of system - that had moist air over the top and then it was cold underneath. This is just cold, showery stuff coming up from the Antarctic, so it's unlikely to reach warning levels.

"However, we are just keeping an eye on it, because it could possibly cause some disruption to transport if it falls in the urban areas."

A few showers were likely to hang around this week, mostly in the east and south of the North Island, falling as snow about the higher roads. Elsewhere, skies would gradually clear.

The strong southerly flow would also bring heavy swells to exposed coasts over the next couple of days before easing.

However, there was a chance large swells could persist around coastal Hawkes Bay and Gisborne until the end of the week.

WeatherWatch forecaster Philip Duncan said Monday was the shortest day of the year, so the cold weather system was timely.

"It's not a big snow maker - but it certainly is a significant shot of cold air from our polar part of the planet," he said.

"No matter where you live in New Zealand temperatures will drop on Monday or Tuesday."

WeatherWatch was anticipating severe frosts, with Mr Duncan saying cold rather than snow would be the main focus this week.

"Last week ended warm for many - this week will not be the same. Welcome to winter - and to the start of the coldest, darkest eight weeks of the year."

Monday's forecast

Whangarei:

Few morning showers, then fine.

Freshening southerly. High 14C Low 6C.

Auckland: Few morning showers, then fine.
Freshening southerly. High 13C Low 4C.

Hamilton: Few morning showers, then fine.
Freshening southerly. High 12 Low -2C.

Tauranga: Few morning showers, then fine.
Southerlies. High 14C Low 3C.

Wellington: Showers, clearing for a time morning.
Strong southerly. High 9C Low 4C.

Christchurch: Sleety showers and southerlies easing, then fine spells.
High 6C Low -5C.

(Source: MetService)