A thundery Friday could be on the way as unstable weather looms for a large swathe of the North Island. 

MetService has this morning issued a severe thunderstorm watch for Taumarunui, Bay of Plenty, Rotorua, Taupō, Gisborne, Hawke’s Bay and Taihape. 

The watch is from 3pm to 11pm today. 

“A showery unstable air mass is expected to affect the North Island from this afternoon and evening”, MetService said. 

“For inland Gisborne and Hawke’s Bay, inland Bay of Plenty including Rotorua, Taupō, Taihape, and Taumarunui, there is a moderate risk of severe thunderstorms with localised downpours bringing rainfall intensities of 25 to 40 mm/h.” 

Rainfall of that intensity could cause surface or flash flooding – especially in low-lying areas, cause slips and make driving hazardous, they said. 

Meanwhile, autumnal weather is set to arrive this weekend as a biting cold front travels up the country, with temperatures dropping as much as 12C in some places. 

While many parts of the country have been spoilt with warm weather over the past few days, MetService meteorologist Lewis Ferris told the Herald that temperatures are expected to plunge heading into the weekend. 

New Zealanders will need to brace for much cooler conditions as a front moves north up the country today and tomorrow. 

The swing will be less noticeable in the northern regions, particularly the Far North, but in more southerly parts of the country, the cold snap will be particularly pronounced. 

At 7am today the temperature was just 5C in Invercargill, 10C in Christchurch and Dunedin and 12C in Wellington, while Auckland was on a relatively balmy 16C. 

Forecasts show Blenheim is set to drop from a high of 28C yesterday to a high of just 16C today, while temperatures in the capital will fall from 22C to 15C. 

There may be “a little bit” of wet weather as the showery southerlies move north, with localised heavy showers hitting parts of the North Island in the afternoon and evening. 

“The wet isn’t going to be so bad but annoyingly, there is going to be some wet weather,” Ferris said. 

“They’re not going to, like, ruin the entirety of the weekend, but if people are making weekend plans, they will need to make sure they’re dodging those showers if at all possible.” 

Though “not the type of storms that are going to affect everyone”, he warned the central and eastern regions should also prepare for possible thunderstorms. 

“It is something to be aware of if you’re around the region and happen to get caught under something very heavy. Whether you’re driving or not, the idea is just to stay where you are.” 

Tomorrow, a high-pressure system will cover the country and bring much calmer conditions, with southerners set to enjoy mainly fine conditions after a wet end to the week. 

But the settled weather is expected to be short-lived as crisp spells return on Sunday. 

“We do have more cold air push in from the south through Sunday so again we’re going to see those temperatures drop once again and look to be quite cool as we head into the new working week,” Ferris said. 

The forecast for Monday anticipates a continuation to Sunday’s cold wave, with temperatures sharply falling by several degrees in most parts of both the North Island and the South Island.