A day of 280 lightning strikes for Whanganui, with colder winter ahead

Unsettled weather brought rain, hail, thunder and lightning across Whanganui over the past few days. Photo / File

The Whanganui region was struck by lightning 280 times in the 24 hours to noon Friday, and has already had more rain than usual in May.

Thunder and lightning and bursts of heavy rain and hail have swept across the region, as a succession of troughs moves across New Zealand.

Despite this there have been no weather-related callouts for Whanganui fire crews, senior station officer Craig Gardiner said.

But Gonville resident Jo Morris had an unnerving experience on Thursday night. As she turned on her kitchen light the bulb flew across the room and broke, and power in the house went off.

"It gave me a big fright," she said.

A storm was raging outside and lightning had struck a fuse in a power pole. Hers was the only house affected and it was too dark to find her torch. Luckily her neighbour helped out.

Contractors put her power back on about 10pm and a Powerco spokesman confirmed there have been a number of outages due to lightning strike across the region during the last two weeks.

Winds have been northwest but will turn to the southwest today, MetService forecaster Stephen Glassey said.

They feel cold because a cold air mass is moving over New Zealand. The strongest gust this month was 81km/h on May 22.

The past two weeks have certainly been soggy. It has rained every day since May 11, with heavier falls on May 13, 22 and 23. The heaviest, 24mm, was forecast for May 25.

Total rainfall for the month so far is 108.2mm, well above the May average of 73mm.

The heaviest rain recorded at Whanganui Airport was 7.2mm from midnight to 1am on May 25. Any amount over 6mm an hour is counted as heavy rain, Glassey said.

The rain has come with thunder and lightning, often in short, local bursts, and sometimes with hail. Some hail has measured 9mm in diameter - a 20mm diameter is big for hailstones.

Winds are expected to turn southwest today, and increase. The highest parts of the State Highway 1 Desert Rd between Waiouru and Turangi have been closed by snow at times, and more is expected on May 27.

Mt Ruapehu's Whakapapa ski area has nearly 1m of snow, and is expected to open on June 2.

The southerly weather has brought some big southwest swells, with waves of 5m to 6m along exposed parts of New Zealand's west coast.

"Whanganui is a bit sheltered from that, but there have still been some reasonable waves," Glassey said.

Forecasters expect this winter to be colder than the relatively mild 2016 and 2017 winters.

Glassey said there have already been more southerly outbreaks across the country. They have cooled sea temperatures.

"Colder sea temperatures correspond to colder weather."

Sea temperatures were abnormally high during summer and early autumn - in the low 20C. They have since dropped to 16C on the Whanganui coast.