Humidity easing, but not for long

A kite surfer takes advantage of the stormy conditions on the Waitemata Harbour off St Heliers in Auckland. Photo / Paul Estcourt

Had about enough of the unbearably hot and muggy weather? Don't worry - the extremely high humidity levels are expected to ease today.

Auckland, Coromandel, Nelson and Christchurch were just some of the many places that sweated and sweltered in 100 per cent humidity yesterday.

MetService duty forecaster Sarah Sparks said the misty and sticky conditions were typical of high humidity levels brought by Cyclone Zelia, which hit yesterday.

"By the time it got to us it was no longer classed as a tropic cyclone ... but it brought with it a warm northerly air mass across the country."

Ms Sparks said the mist was caused by the humidity because the air was full of water.

"It's a bit like when you're having a shower and the bathroom clouds up ... it was also raining a bit in Auckland, adding to the low visibility."

Many people would have trouble sleeping because of the humidity, she said, but the sticky weather was expected to be replaced by fine weather today.

"Humidity levels normally peak at night," Ms Sparks said. "But we've got a low pulling off of the country and we'll get a westerly coming in behind. That westerly should hopefully lower those humidities and the temperatures."

WeatherWatch chief analyst Philip Duncan said 100 per cent humidity meant the air was saturated.

"So when you sweat it just sticks on your skin and can't evaporate off. If you want to get comfortable, your only option is to have a cold shower, but about five minutes after getting out that you'll be sticky again."

Although humidity could reach complete saturation at any time during the year, it was particularly unpleasant when coupled with the high temperatures New Zealand had been reaching lately, he said.

"It makes it very difficult to do even the smallest tasks."

But even though it would clear today, Mr Duncan said, the nice weather would not last the week and Big Day Out revellers would be rocking out in another wave of high humidity.

"The amount of sweat there is going to be gross ... Unfortunately we're expecting a muggy, dreary weekend which will kick in on Friday or early Saturday."

The heavy rain and strong winds Zelia brought wreaked havoc around the country last night.

Heavy rain caused the Fox River between Greymouth and Westport to burst its banks. Police and fire crews evacuated people from their Fox River settlement baches as a precaution.

The downpour also caused a mudslide at Uranium Pt on the West Coast yesterday afternoon which took three hours to clear, causing traffic delays.

Marlborough and the Bay of Plenty's rivers and drains were threatened by the 100mm of rain expected to fall there last night.

Environment Bay of Plenty's rivers and drainage manager, Ken Tarboton, spent yesterday checking pumps were clear so they were not flooded.

"Our staff are actively monitoring the situation using tools such as our recently installed weather radar and forecast-modelling systems as well as keeping in close contact with the MetService," he said.