Live weather: Another icy morning, with temperatures set to dip further

Update from Metservice’s John Law as cold weather hits NZ

MetService says it's been one of the coldest mornings of the year and it's set to continue for the next two days.

Mt Cook at minus 9 degrees Celsius, Tekapo at minus 7 and Wanaka and Blenheim (both -5) had the coldest starts to the day in the country.

Temperatures dropped to freezing in some parts of South Auckland overnight.

Meteorologist Luis Fernandes says Ardmore Aerodrome hit zero degrees at 3am on Wednesday, and was sitting just below 2 degrees around 5.30am.

It appeared to be an outlier, with most temperatures between 4 and 6 degrees, however, he said the day was shaping up to be Auckland's chilliest so far this year.

Temperatures as far north as Auckland and Northland would be even colder overnight tonight, possibly producing frosts, meteorologist John Law says.

Taumauranui would possibly be at -6degC and Hamilton at -4degC on Thursday.

"So cold, frosty and really chilly."

Some highways are shut on Wednesday, including State Highway 1 between Waiouru and Rangipo (the Desert Road) and the Remutaka Hill Road near Wellington.

Warning about power supply as consumption at all-time high

Transpower, which manages New Zealand's power grid, has issued a warning that there might be an energy shortfall this week.

Executive general manager operations Chantelle Bramley said: "We are actively managing the tight balance between supply and demand during this cold snap."

She said during Wednesday morning's peak, it saw the highest-ever electricity use at 7247 MW.

Late last night a generation unit had a fault and was removed from service.

"The power system remained secure and there was no impact on consumers."

She said Transpower was working closely with the industry to ensure that there was enough generation offered to cover the record demand.

"At this stage we do not anticipate any impact on electricity supply to consumers."

It has put out a customer advice notice, which says a national energy shortfall or low residual generation had been identified on Friday from 7.30am until 8.30am.

It had earlier issued warnings this morning between 7.30 and 8.30, this evening between 6pm and 7pm and Thursday morning between 7.30am and 8.30am.

Pressure on elderly Kiwis during cold snap

Meanwhile, an advocate for older people says many senior citizens are having to spend most of the day in bed because they can't afford to heat their homes.

Age Concern Canterbury chief executive Greta Bond told Morning Report older people on fixed incomes were having to make real choices every day about whether they will be warm or fed.

"Every week we're encountering people who are really struggling. Renters are in a particularly precarious position because they may be spending 60 or 70 percent of their pension on rent.

"It's actually a real crisis for people. I don't think people really understand or like to think that we have older people who are actively living in poverty in our country," Bond said.

Many people were resorting to spending most of their day in bed with negative consequences.

"They might get up for a little bit in the middle of the day when it's the most warm, probably not at all this week. They might just wake up in the morning, get themselves a cup of tea or something, and then just stay in bed the whole day.

"That's so bad for them in terms of their health, their physical health, their mental health, their social connection, but definitely staying in a really constricted life because they can't go out. And they might not even leave their bedroom."

See how the morning unfolded below.