"There could well be some thunderstorms, likely in the afternoon and evening – there's a chance of thunder, strong wind gusts and heavy downpours."
It's poor timing for the Auckland Marathon which is scheduled to begin at 6am today, with the half marathon runners beginning their race at 6.50am.
Marathon organiser Amy MacCormack told the Herald that runners should prepare with warm and wet weather clothing.
"Race organisers are in close liaison with the relevant authorities and will continue to monitor conditions and send the appropriate advice to participants."
It's the first time since 2019 that international athletes have been able to compete in the event after border restrictions were lifted this year - but with unfavourable conditions forecast all day it could be a challenging race.
"All in all, it's not looking too flash and that goes for much of the country," Pyselman said.
The unsettled conditions are due to a northerly airmass that has settled over Aotearoa bringing the humid, muggy conditions of the past few days.
"There's going to be heavy rainfall for much of the day – it's not great running conditions because it's going to be wet and muggy with a brisk northerly," Pyselman told the Herald.
MetService issued a severe thunderstorm warning for Gore and Southland yesterday evening saying severe thunderstorms had been detected near Mataura, Edendale and Wyndham.
The National Emergency Management Agency advised that as storms approached people should take shelter, preferably indoors away from windows and avoid sheltering under trees if they are outside.
Pyselman told the Herald the thunderstorms could continue into the evening and it was probably best to stay inside.
"You're unlikely to be hit, but obviously don't go outside holding a metal rod or something - golfing probably isn't the best idea."
Further north in Wellington, high winds saw disappointed fans turned away at the doors of Six60's show at Sky Stadium. The band said they were "gutted" to have had to make the difficult call to postpone but that fans' safety was paramount.
"We encourage fans that are able to hang on to your ticket and we'll see you [Sunday]."
In Auckland, yesterday brought lightning to much of the region - out of 1290 lightning strikes across Aotearoa 109 were in Auckland - some frighteningly close to homes.
Residents in Mount Albert reported a lightning bolt striking "very close" to a home, as torrential rain bucketed down across the city.
Residents said the strike occurred close to a home on Malvern Rd, and another person said they had experienced sparks flying at their property on Springfield Rd.
