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Residents in the West Coast town of Kumara on Tuesday watched lights from the biggest solar storm in six years cast a strange grey-white glow across the sky.
Weather observer Gordon Sylvester first spotted the strange glow about 10pm, coming from the south-south-east. It got stronger as the night wore on, and was still there at 3.25am, when he got up for another look.
He said there was no source of light contamination, and the street lights were a more orange colour. Light reflection from Greymouth is to the north-west.
"I know what I'm looking for - I saw the big one in Nelson 12 years ago," Mr Sylvester said.
A similar white light was also seen at the weekend over Banks Peninsula.
The sun is currently bombarding the Earth with radiation from the biggest solar storm in more than six years, probably with more to come.
The solar flare started about 5pm on Monday, and has caused spectacular shows of the northern lights in parts of Europe.
The National Oceanic and Atmospheric Administration's Space Weather Prediction Centre in Colorado said the radiation was mostly a concern for satellite disruptions and astronauts in space.
It could cause communication problems for polar-travelling aeroplanes, space weather centre physicist Doug Biesecker said.
Radiation is expected to continue until tomorrow.
In 1989, a solar storm caused a massive blackout in Quebec. It can also pull the northern lights farther south.