Wellington's unusual rumbling thunder early this morning certainly sounded like an earthquake - and may have even registered as an earthquake.
Volcanologist Steve Sherburn said thunder can sometimes appear as seismic activity on GeoNet's seismographs.
This phenomenon was also seen last weekend near Tongariro National Park, he said.
"When the [sound] wave hits the ground, some of the energy travels into the ground and becomes a ground wave, which the seismic sensor can pick up."
Two small blips on GeoNet's Wellington seismograph were recorded at about 4am this morning.
The rumbling thunder was caused by a rare form of lightning storm, which also brought cloud-to-cloud lightning bolts.
MetService meteorologist Andy Downs said the spectacular storm formed from wave cloud, when strong winds lifted warm moist air from Australia over the Kaikoura and Richmond ranges.
He said people woken by the strikes, starting just after 4am, might have thought the long thunder booms sounded more like the rumble from a landslide or earthquake.
One or two bolts were also seen near Masterton overnight, and several more strikes might happen during the day, Mr Downs said.
Yesterday, the MetService issued a severe weather watch for the capital, predicting gusts of up to 110kmh.
A severe weather warning was also issued for the Wairarapa and up to the Hawke's Bay region where winds of up to 140 kmh were expected.
Mr Downs said the gusts could potentially damage property, trees and powerlines and would continue through the day, before easing overnight.
Central Fire Service shift manager Mike Wanoa said there had been reports this morning of minor damage to roofs from the gusts in Featherston, but no major damage.
In Wellington, the northern suburbs experienced higher rainfall overnight, with 17mm of rain falling in Tawa and 9mm recorded at Wellington Airport.
The rain should ease early this morning, with only the possibility of a few millimetres falling in the northern suburbs.
While the front would move over the capital by the end of the today, the weather for next week was not looking to improve, Mr Downs said.
Showers were forecast for Monday, and another front would move over the city on Tuesday, bringing gale-force winds.
- © Fairfax NZ News