Severe marine heatwaves are poised to hit the bottom of the South Island triggering downpours and potentially harming marine life.
Sea surface temperatures will be at 4 degrees or more above average, MetService oceanographer Dr Joao de Souza says, particularly along the West Coast, Stewart Island and the Otago peninsula.
"Surface temperatures are forecast to reach 18.4 degrees, compared to the 13.5 degree average – a difference of almost 5 degrees,” de Souza says.
Higher ocean temperatures will heat the air above the moana according to de Souza, increasing humidity and triggering downpours.
The heatwaves may also bring harm to marine life.
“Last year, a similarly warm marine heatwave in Fiordland reached great depths and caused widespread bleaching of sea sponges, and recent West Coast kelp disappearance has also been attributed to marine heatwaves.” Dr de Souza added.
The MetService says regions in the north won't be spared from the poor conditions, with severe weather watches and warnings issued from the Coromandel, to Northland.
Rainfall and wind strength warnings are in place for Wednesday and Thursday in Tai Tokerau, while Auckland, Great Barrier Island and Coromandel Peninsula will have to batten down the hatches through to Friday.
Northwest Tasman has potential heavy rain on Thursday and Friday, with a lesser chance Otira and Fiordland may also be hit by downpours.
