Country swelters under high humidity and it's not going away yet

Sub-tropical air over New Zealand is leading to balmy temperatures and high levels of humidity. It also contributed to fog, grounding planes and stranding travellers. Photo/via Twitter

New Zealand is sweltering under unusually widespread high levels of humidity.

Today many towns and cities across the length and breadth of the country have recorded tropical 100 per cent levels of humidity.

At 9.15am humidity in parts of Auckland and Christchurch had reached 98 per cent.

In Wellington and Dunedin, where fog has disrupted air travel, humidity levels had reached 100 per cent.

Elsewhere throughout the North Island, towns and cities are recording levels at 90 per cent or greater.

MetService forecaster Peter Little said it was abnormal for the entire country to be saturated in high humidity.

"But we have had this northerly flow that's allowed the moist air from the sub-tropics to push down over the whole country."

Overnight temperatures were also balmy, as Tauranga, Auckland and Napier recorded around 18C.

Low cloud is still hugging the east coast of the South Is. https://t.co/rcECVuGXOw ^PL pic.twitter.com/vwoOMq9mtu

— MetService (@MetService) March 29, 2017

Little said there would be little respite from the humidity until the air started to dry out by the weekend.

"We're stuck with high humidity levels for a few days yet but it's not going to be as bad," he said.

"That means in many places where there are light winds there will be fog in the morning and low cloud but the sun should win through for much of the weekend."

But come Sunday, moisture-laden air from the tropics would return, spreading across the entire North Island and top of the South Island for the start of next week.

On top of this the remnants of ex-tropical cyclone Debbie appeared on some models to be drawn down towards New Zealand ahead of a front bringing wet weather.

This would increase humidity levels even more, said Little.