Wet start to day for most places, worst weather forecast for lower South Island

There was a wet start to the day for most places. Photo: RNZ / MARIKA KHABAZI

It is a wet start to the day for most of the country with the worst of the weather expected in the lower South Island as MetService issues a severe thunderstorm watch.

It is in place until 9pm on Tuesday across Central Otago, Dunedin, Clutha and Southland which are expected to see scattered showers and isolated thunderstorms this afternoon.

Most of the downpours are forecast between 2pm and 9pm which could see localised downpours with rainfall rates of 25 to 40 millimetres per hour.

MetService warns the intensity could cause surface and flash flooding along with slips.

Tuesday's emojicast:

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— NIWA Weather (@NiwaWeather) February 17, 2025

MetService meteorologist Katie Hillyer said the South Island was seeing a switch in weather with a low coming up from the Tasman which was bringing a few bands of rain.

"So what that will look like over the South Island over the next couple of days is periods of rain, really the worst of it today where we've got period of heavy rain and then quite a few risks of areas of thunderstorms this afternoon," Hillyer said.

Between 80 to 110 millimetres of rain has fallen across the Tasman ranges already over the last 24 hours.

It follows orange heavy rain warnings which have now expired across Gisborne, the Coromandel Peninsula and the Tasman District.

She said yesterday's weather came from a feed of moisture from the north.

"We've had a lot of systems from the south so far this summer so this does feel like quite a change. All of the rain that the upper North Island had over the last couple of days, that was due to a low from the tropics that was just dragging that extremely humid moist air down over us and raining onto the likes of Coromandel and Gisborne," Hillyer said.

Hillyer said both areas saw higher rainfall totals with persistent downpours.

"Within a 24 hour period, 9pm to 9pm last night, we saw for Coromandel about 180 millimetres. If you take that out a couple of hours either side we were approaching or just getting over 200 millimetres. Gisborne was very similar sort more in that 160 to 180mm but again if you extend that period out just a little bit beyond that 24 hours, you're getting out to around closer to 200mm," Hillyer said.

⚡Severe Thunderstorm Watch Issued⚡

⛈️Thunderstorms could become SEVERE with localised DOWNPOURS (25-40mm/h) this afternoon in southern areas.

⚠️This can cause surface flooding and dangerous driving conditions.

Keep up to date here: https://t.co/qHyE5zzql5 pic.twitter.com/3hnA6kfeMA

— MetService (@MetService) February 17, 2025

Westland was forecast to likely see the most downpours today and over the next few days, she said.

The weather is forecast to pick up on Wednesday except for the west and top of the North Island where scattered showers are predicted.

Meanwhile, in the South Island it is expected to be mainly fine in the northeast with occasional showers else where. Some areas will see heavy rain early on.

Muggy nights in Wellington

Meanwhile in Wellington and the wider region, it has been a sleepless night for many as temperatures range between 19 to 20 degrees Celsius.

Muggy morning?️

For some spots, it may have been a restless night with temperatures staying above 20°C‍

And with the mercury already well into the 20s before 8am, the morning commute across the North Island may have felt a bit sweaty too pic.twitter.com/SRg2x88qYi

— MetService (@MetService) February 17, 2025

Hillyer said the warmer weather was coming from the sub tropics and was a combination of the heat and cloud cover keeping overnight temperatures very warm.

"The part that makes this particularly uncomfortable as well is the high humidity and that is acting to also just make it feel a bit stickier and a little uncomfortable," Hillyer said.

Wellingtonians could expect to have another couple of restless nights until Thursday or Friday when high pressures would push humid weather out and replace it with fresh air, she said.

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