Sticky outlook: Muggy days and nights ahead as humid weather system nears NZ

• A north-westerly flow from Thursday is expected to bring rain and warm, humid conditions to northern centres late in the week.
• In Hawke’s Bay, temperatures are forecast to hit 30C in Hastings on Friday and Saturday, amid an early summer drought.
• A Niwa forecaster expects the unsettled westerly pattern to persist past Christmas, before a shift to La Nina-like patterns from New Year.

Much of the North Island is in for a hot and sticky end to the week, courtesy of an incoming weather system that’s also likely to spell widespread rain on Thursday.

It’s the latest in a long-running pattern of westerly flows that have pushed Hawke’s Bay towards drought while bringing unsettled weather elsewhere – and is likely to persist past Christmas and to 2025.

MetService forecaster Thapi Makgabutlane said this week’s low-pressure system, arriving from the northwest on Thursday, would bring with it a surge of warm, moist air.

In Auckland, rain that could worsen to heavy downpours on Thursday would be followed by cloudy, humid conditions on Friday, with temperatures forecast to reach 26C.

Other northern centres were similarly forecast to experience warm and muggy weather on the back of the system, with Whangarei and Hamilton both forecast to hit 27C on Saturday.

“We’re also looking at [overnight] temperatures in the mid to even high teens for that part of the country ... so there are some muggy nights ahead.”

At this point, MetService was forecasting a low probability of rain reaching warning amounts around the eastern ranges of Bay of Plenty on Thursday.

A separate front arriving in the west and south of the South Island also posed a low chance of severe rainfall for Fiordland and the far south of the Westland District.

That’s been a familiar picture since spring, with high pressure to the north-east and low pressure to the south-west driving a succession of rainy, westerly fronts onto New Zealand.

For eastern regions like Hawke’s Bay, where these westerly winds have arrived stripped of moisture, the result has been parched soils and high fire danger.

Coastal areas of Hawke’s Bay now met the criteria for drought, while swathes of the region were classified as very-to-extremely dry.

The region is forecast to get scorching hot temperatures this week, with the mercury to reach 30C in Hastings on Friday and Saturday.

From around New Year, however, Niwa is expecting a shift to more “La Nina-like” conditions – raising the odds of more north-easterly flows and subtropical rainmakers.

Until then, Niwa forecaster Chris Brandolino said Kiwis were in for more patterns like this week’s, adding the forecast for Christmas itself wouldn’t be clear until 10 days from now.

“Westerly quarter winds will probably be theme for the rest of the month.”

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.

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