Thunderstorms and downpours possible for Auckland and Northland

Thunderstorm watches have been issued for the top of the country, with downpours of 25-40mm per hour possible.

Northland’s watch is underway and lasts until 9pm today, while one for Auckland and Great Barrier Island was for 11am-9pm.

MetService said the watches carry a moderate risk of severe thunderstorms with localised downpours of up to 40mm/h.

“Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.”

Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain, MetService said.

Heavy rain watches for Northland, Auckland, Great Barrier Island, Waikato, Waitomo, Taupo, Taranaki, Taumarunui and Tongariro National Park kick in from 9pm, lasting until 1am Wednesday.

It comes as muggy nights are forecast for the North Island as a “subtropical air express” brings warm, moisture-laden Pacific air.

MetService says a humid northerly flow will gradually spread across the island at the start of this week.

Meteorologist Paris Marshall told the Herald yesterday that Whakatāne and Whitianga were forecast to have “sweltering” overnight lows of 17C tonight.

Marshall said the incoming weather was being driven by a separate system from the Tasman Sea.

“It’s just been whirling away for a while, collecting all this moisture from the ocean.

“And it’s decided, oh, let me just head over to New Zealand ... which is a bit unfortunate for those who have already suffered quite wet weather.”

The incoming weather follows a dramatic Saturday afternoon when thunderstorms unleashed torrential rain and large hailstones across parts of the North Island.

Lightning strikes over Auckland during a severe thunderstorm warning on Friday. Photo / Brita Barton

In Auckland, large hailstones damaged vehicles in the Waitākere Ranges, while heavy downpours caused flooding on the North Shore.

The storms also disrupted flights, caused power outages and delayed the Auckland FC-Wellington Phoenix match.

MetService detected more than 5000 lightning strikes on Saturday, mostly across the North Island.

Meanwhile, severe thunderstorms swept through parts of Canterbury yesterday afternoon, prompting a warning for the Hurunui district.

Thunderstorms brought heavy rain, hail and lightning to parts of the North Island on Saturday. Photo / Anika Guthrie

Marshall said there was a moderate risk of thunderstorms across central and northern parts of the North Island today.

The forecast could change as the weather system developed, she said.

Further thunderstorms are possible on Tuesday, particularly in Northland, Auckland, Coromandel and Bay of Plenty, with heavy rain also possible in the lower North Island and Nelson-Tasman.

The South Island will largely escape the humidity until Wednesday, when the system is expected to “push off” from the North Island, bringing wetter and muggier conditions further south.