In December, MetService recorded a mean temperature of 17.7C, compared to the climate mean of 16.9.
It was a similar story in January and February, with a mean for January of 18.7 and 17.9 in February, compared to the respective climate means of 17.9 and 17.8.
Niwa principal scientist Chris Brandolino said the total amount of rainfall in Whanganui was more than double the average for the season.
The increases in temperatures were caused by the combination of abnormally low atmospheric pressures in the north of the North Island and abnormally high pressures at the southern end.
These two pressure systems, which turn in different directions, worked like two cogs in producing a warm airflow moving across the region from the north and northeast.
“That airflow in your neck of the woods would be a warm wind, air coming off of the central plateau and other ranges to the east,” he said.
This airflow was aided by New Zealand being under the influence of the La Niña Pacific climate driver over the summer, as it had been for the last three years.
La Niña meant the water temperatures in the Pacific Ocean had been abnormally warm for those three years.
“Because we’re an island nation, we’re really at the mercy of our ocean temperatures, if our ocean temperatures are running higher than usual, so will our air temperatures,
“What that does is it has a flow-on effect atmosphere and that causes certain weather features to set up camp more than usual, and that’s what happened for us.”
Federated Farmers Wanganui dairy chair Andrew Pearce said these conditions made for a challenging start to the summer for local farmers.
“Early summer was very challenging because saturated grounds made it hard for people to get crops in and get crops established and also to get supplements off,” he said.
However, from January onwards the continued rainfall made the rest of the season easy on farmers and their wallets.
“From a pastoral point of view it’s been great, we’ve had plenty of moisture which has allowed people to grow a lot of grass which has meant that it’s been a low-cost summer.”
Pearce is a cattle farmer and, due to the amount of rain, he needed to use little supplement, such as silage, to feed his stock.
Looking forward to the rest of the year, he said farmers would be hoping for a relatively dry autumn.
“If we go in wet and have a wet winter, everything becomes waterlogged [and] it can set you up for a challenging winter.”
He said, if that happened, it would be a difficult season of dealing with slips and trying to stop cattle from damaging the waterlogged soil.
It appears farmers may get their wish for a drier run-up to winter, with March appearing to have brought a change in conditions.
Brandolino said the country was no longer under the influence of La Niña, with it being classified as in a neutral position on the El Niño Southern Oscillation (ENSO).
With El Niño expected to fully arrive by June, he said to expect a change from the three record-warm winters we’ve experienced back to back to back.
“Our expectation is as we get closer and closer to what we think will be an El Niño, we’ll see more of a southerly to southwesterly wind flow,” Brandolino said.
The change in wind flow could allow for sharper and more frequent cold snaps than we’ve become to accustomed too.
However, ocean temperatures around the country are unusually warm currently which may take the edge off of those cooler temperatures.
