Heatwave weather: New Zealand boils as sea temperatures surge over 20C

New Zealand is burning on land and boiling at sea as a brutal Australian heatwave sinks its red claws into the country.

A scorching summer blast has seen the mercury go over 35C around Aotearoa - with fears this could rise to over 40C in parts of eastern New Zealand.

But there's no respite or relief to be found in the cool ocean, as sea temperatures surge to over 20C around the North Island.

"It took a while, but sea temperatures around New Zealand have really warmed up!" NIWA says on Facebook.

"If you're headed to the beach this weekend, 20C+ is common around the North Island.

"Sunday will be the hotter of the two weekend days, so make the most of the heart of summer if you can!"

And NIWA warns the hot sea temperatures in the Pacific could lead to more destructive weather patterns in the second half of February.

Due north of New Zealand, a persistent patch of warmer-than-average ocean temperatures could send strong low-pressure systems down towards us.

"Cool seas that were once present here north of Australia have been replaced - replaced by warmer seas. And that means there's going to be a change overall in what's driving our climate," NIWA meteorologist Ben Noll says on Facebook.

"What that creates is a favourable environment for lift and rising motion in the atmosphere. And when you have that, you have rain and thunderstorms.

"So that creates an environment that's positive towards the formation or generation of tropical weather systems like tropical cyclones."