Powerful solar storm activity is forecast for Saturday which could interfere with New Zealand's electricity supply, Transpower says.
It comes as the US National Oceanic and Atmospheric Administration (NOAA) revealed "extreme" (G5) solar storm conditions have been observed for the first time since 2003.
The US NOAA said several strong flares had been observed in the past few days which were "associated with a large and magnetically complex sunspot cluster... which is 16 times the diameter of Earth".
Solar flares happen when "charged particles are accelerated by processes at or near the sun" and "arrive in enough quantity at Earth", the US government agency said.
A grid emergency notice was on Saturday issued by New Zealand electricity transmission company Transpower. The notice was initially valid from 9am until midday but subsequently extended to 6pm.
Transpower warned this was due to a "geomagnetic induced current event" which resulted in multiple lower South Island circuits being temporarily removed.
"This has been done in a way to avoid impact on consumers' electricity supply," the state-owned company said in a statement.
"At this stage, Transpower does not anticipate any impact on New Zealand's electricity supply to consumers.
"Transpower will continue to monitor the situation and provide updates as required."
New Zealand's National Institute of Water and Atmospheric Research (NIWA) said the storm was expected to peak on Saturday night.
"While most solar storms don't cause much impact, this is an *unusually strong event* & it pays to be prepared.
"It has the potential to affect communications, GPS, satellite navigation & power grids," NIWA added.
The space storm resulted in the early morning sky erupting in a colour display as a stunning aurora lit up parts of the country.
It comes as Kiwis woke to another freezing morning, with a cold snap sending temperatures plummeting across the country. Saturday's grid emergency notice came just a day after Transpower warned of possible electricity supply shortages amid freezing temperatures.
As of 10:45am, Alexandra was the coldest area of the country at 0.1C - having dropped to -3.5C overnight.
