Thundery start for North Island, south in for 'a rumble or two' later

It has been a "thundery morning for the North Island", according to MetService, with the South Island also in line for a "rumble or two" this afternoon.

The forecaster said thunderstorms were observed over central western parts of the island this morning.

It said bursts of heavy rain, strong wind gusts and hail could be expected over the coming hours.

Shortly before 10am, strong wind watch was issued for Coastal Southland, Stewart Island, and coastal areas of Otago south of Oamaru for 13 hours from 2am to 3pm tomorrow.

MetService said those areas could expect "gale force west to southwest winds spreading northwards, then easing from the south".

"Winds may approach severe gale in exposed places. Moderate chance of upgrading to a warning," it said.

It said thunderstorms in the North Island should dissipate by midday today, but rain would remain.

"In contrast, from afternoon is when South Islanders in the west should start to hear a rumble or two," it said online.

MetService meteorologist John Law said there were some "fairly active showers moving across the North Island this morning".

"They'll clear away, then drier and brighter this afternoon," he added.

However, Law said down in the South Island the next bout of "wetter weather [is] moving up".

Law also said it had been a "chilly start" today, with temperatures back down below freezing for places including Tekapo.

"This afternoon some fairly active, even thundery conditions back in toward parts of Southland and up past that western coast."

It followed wild weather conditions brought on by Cyclone Vaianu, including red-level warnings due to the forecasted risk of threat to life.