Here comes the heat: Mercury rising fast over NZ

The mercury is rising fast over much of eastern New Zealand as a blob of warm air – care of Australia – fires up the back half of our weekend.

The warm mass, channelled over New Zealand by a big high pressure system parked over the Tasman Sea, is expected to drive temperatures in many places above 30C this afternoon.

Incredibly, the heat was already being felt in the early hours of today – reaching 24C in Dunedin at 3am.

By 9am, temperatures had reached 23C in Oamaru and 25.5C in Fairlie – and by 10.30am, Dunedin was sitting at nearly 29C.

The hottest spots in the country today would be Blenheim (32C), Hastings (31C) Christchurch (30C), Ashburton (30C), Masterton (30C) and Napier (30C).

Forecasters would be closely watching for any record-breaking figures.

New Zealand’s hottest November temperature on record occurred at Lake Coleridge (35.6C, 1920) followed by Gisborne (34.8C, 2016).

Niwa reported several spots in inland Otago might have hit record figures even yesterday – they included Clyde (32.5C), Alexandra (32.2C) and Windsor (30.8C).

“Even in places like the Tauranga, we’re looking at 28C today, while we’ll probably get up to 26C in Taupo,” Metservice meteorologist Andy Best said.

“In Auckland though, there’s a bit of regime of cloud from western parts of the region, and a southwesterly flow, which will mean it only makes it to about 21C today.”

Temperatures in Hastings are forecast to climb to 31C this afternoon. Photo / NZME
Temperatures in Hastings are forecast to climb to 31C this afternoon. Photo / NZME

Best said the big temperatures along the East Coast reflected the “rather large area” of the high over the Tasman.

Its size meant that over recent days it had been able to channel warm air from the hot, dry, central part of the Australian continent, down over south-eastern New South Wales, across the Tasman, and then straight into the lower part of New Zealand.

“As it travels across the Tasman, however, it does get modified – and that why we don’t see the those really high temperatures.”

The ridge was expected to lie over New Zealand for much of tomorrow, bringing mainly fine weather and warmer than normal temperatures to many parts of the country.

A front approached the far south of the South Island late Monday, moved slowly northwards onto the South Island on Tuesday and becomes slow moving on Wednesday.

Later, during the second week of November and into the middle of the month, some strong fronts were possible in the South Island, bringing rounds of heavy rain and an increased risk for areas of flooding, especially in the west.

MetService predicted that, overall, monthly temperatures for November would end up above average for northern and eastern regions of both Islands, with prevailing mild northwesterly winds and near-normal rainfall for most places.