Wet and warm start to the year gone as the chill starts to hit

After a scorching, record-breaking summer the winter chill has arrived, and it may take a while to warm up again.

The first six months of the year are a story of warm and wet, while the latter half is predicted to be cooler and more "changeable".

Figures from Niwa showed between January and June, record or near-record high mean monthly temperatures were reached 163 times.

Conversely, there were just three record or near-record low mean monthly temperatures.

"In other words, for every record or near-record cold temperature, there have been about 54 warm ones," Niwa meteorologist Ben Noll said.

Those temperatures made it the fifth warmest start to any year on record, sitting behind only 1998, 1937, 1999 and 2016.

The warm 🌡️🌡️🌡️

From January-June 2018, record or near-record high mean monthly temps were reached a staggering 163 times.

During the same period, there were just 3 record or near-record low mean monthly temps.

That's a ratio of 1 cold extreme for every 54 warm ones. pic.twitter.com/TrT28GPa2N

— NIWA Weather (@NiwaWeather) July 4, 2018

The warmest months were January to March, while April to June were near average.

January was the country's warmest month on record at 3.1C above average.

Noll said the high temperatures were pushed along by the Tasman Sea and New Zealand coastal marine heatwave, and La Niña's northeasterly winds.

"The marine heatwave represented one of the largest ocean temperature anomalies in the world. As an island nation where the seas go we go. If there are above average temperatures in the water, we get that on land.

"Combine that with La Niña driving warm winds from the tropics and it is almost the perfect storm for abnormal warmth."

The wet 🌧️🌧️🌧️

All of New Zealand's main centres, aside from Dunedin, have experienced more wet days than normal from January-June 2018.

Auckland has led the way with 78 wet days so far (the normal amount is 61). Hamilton is close behind at 70. pic.twitter.com/MK5DQwDZ8s

— NIWA Weather (@NiwaWeather) July 4, 2018

New Zealand has not had a month with below average nationwide temperatures since January 2017, or in 18 months.

While it was a warm start to the year it was also very wet.

Every main centre, with the exception of Dunedin, had more wet days than normal.

Auckland led the way with 78 wet days - when more than 1mm fell - compared to an average of 61, with Hamilton close behind on 70 compared to 54.

Tauranga had 61 wet days against an average of 49, Wellington had 60 compared to 56, and Christchurch had 53 compared to 41.

February was particularly wet for the country's largest city, Auckland, with 16 wet days against an average of seven.

Noll said that was also linked to the marine heatwave, and a month when the country experienced two ex-tropical cyclones.

"Warm seas add more vapour to the atmosphere. So when we had more tropical cyclones come down to New Zealand the warm seas helped sustain and feed them."

With the La Niña systems having subsided there were no particular "weather drivers" at the moment, Noll Said.

"Those patterns eased in May so temperatures have subsided back to average. We have had some cold snaps but overall it has not been below average."

The weather would be more "changeable" over the latter half of the year, Noll said.

"Over the next several months there will be quite a bit of variability, because the marine heatwave has subsided and La Niña.

"Those things are climate drivers, so now we have very weak drivers.

"Because of that predictions can be more difficult to make, so there may be ups and downs."

However, as we moved into Spring, there was potential for El Nino to form in the tropics, bringing more southwest winds to New Zealand.

"This could mean more stormy out west and drier in the east and north."

There could also be a "sluggish" start to warmer spring temperatures.

"It likely won't be colder than average, there will be cold outbreaks, but it might just be a sluggish start to spring in terms of temperature."