'Seesawing temperatures' as icy blast pushes parts of NZ as low as 2C

Much of New Zealand is set to shiver through one of the coldest nights of the year so far, with temperatures in several regions hitting the single digits – and in some inland areas, close to freezing.

MetService meteorologist Alwyn Baker told 1News the chilly shift was being driven by a front sweeping across the country followed by a sharp southerly flow.

Overnight Monday into Tuesday, most of the country will drop into single digit temperatures.

Auckland and Northland would be the only regions to dodge single-digit lows, with both forecast to reach 10C on Tuesday morning.

Inland areas were set to be much colder, with Hamilton hitting 4C, while Taupō and Taumarunui were at 3C.

Further south, temperatures will fall even closer to freezing. Dunedin Airport and Alexandra may dip to just 2C, raising the risk of a light frost forming.

Temperatures are expected to rebound in the second half of the week, with daytime highs climbing back toward the mid 20s by Thursday.

Baker said the sudden cold could feel dramatic, but that swings like this were common as the country transitioned from summer into autumn.

"Temperatures are gonna be seesawing for a bit, because what's essentially happening is we're changing from summer being more of those systems and air coming from the north, we're swapping over to winter where it's more coming from the south."

While a single cold snap could not be attributed directly to climate change, Baker said a warming atmosphere amplified extremes at both ends.

"When you put more energy into a system, the extremes become more extreme. It’s like a bathtub — if you rock it gently you get small waves. If you put more energy in, the waves get bigger, and closer together. You get those colder temperatures as well as those really hot temperatures."

New Zealand has already warmed by about 1.1C over the past century, according to NIWA’s long‑running seven‑station temperature series, which showed a clear upward trend in national average temperatures. Every year in the past decade ranked among the warmest on record.

Aside from the stark temperature drop, the weather across the country looked stable, Baker said.

"We've got no watches and warnings and nothing on the severe weather outlook until Thursday and that's just one thing, so it's looking like things are gonna be pretty sensible."