‘Rollercoaster’ outlook for spring weather

Spring in Whanganui could bring changeable weather, with a chance of a warm, dry month in October.
Spring in Whanganui is likely to bring a changeable “rollercoaster” of weather with rebounding temperatures and the chance of a La Nina event emerging by the end of the season.
The National Institute of Water and Atmospheric Research’s (Niwa) spring seasonal climate outlook covers weather probabilities for September, October and November in New Zealand.
Niwa principal scientist Chris Brandolino said for Whanganui, the next 10 days would be “a bit of a rollercoaster” of changeable weather and “ups and downs” with regard to temperatures.
“Spring is that season where we are exiting winter and marching towards summer, and during that transition, it can bring a lot of days where it feels like winter and then summer.
“That’s pretty typical for spring because it’s a shoulder season where we’re going from one extreme to another.”
Whanganui’s temperatures were predicted to be average or above average, with rainfall normal or above normal.
“The fronts we’re seeing in the first couple weeks of September could bring a decent amount of rainfall.
“It doesn’t mean every single week or month is going to be the same – some will be dry.”
The regular September rainfall may sometimes be heavy enough to cause flooding.
The first half of September could also bring noticeable wind, with conditions expected to ease to less windy days in the second half of the month.
“Our expectation is that the wind will continue to be something people will notice for the next week to 10 days.”
Brandolino said October looked pretty stable and steady, with more days of warm weather than not.
“There are some pretty strong indications that October could be a pretty dry month potentially, and maybe even a warm month.”
On Niwa’s observation point for Mt Ruapehu weather at the height of the Chateau Tongariro, there was “no snow on the ground” at 1100m.
Looking ahead to November, there could be more of those warmer temperatures.
There was a 50% chance the climate driver of La Nina could emerge by the end of spring – but it was not guaranteed.
“What that would mean for New Zealand is that this type of La Nina could favour high-pressure near and maybe east and northeast of the North Island,” Brandolino said.
“For Whanganui, a La Nina would potentially favour warm and dry conditions, particularly in summer.”
He said by the end of spring and early summer, a La Nina could have developed, which would influence weather patterns.
“We tend to get more northeast winds when we have a La Nina, and if that were to happen, it would favour dryness in Whanganui.”
The next few days could be “pretty breezy” within Whanganui’s city.
Warm temperatures would continue on Monday and Tuesday, with windy conditions expected and a chance of showers.
“It doesn’t look like anything that will cause any major damage, more of a nuisance than anything else.”
Wednesday and Thursday could bring a break from the wind and a drop in the temperatures.
Cooler temperatures are expected for both days.
On Friday temperatures are expected to rise again, and the wind may return and persist into next week.
Eva de Jong is a reporter for the Whanganui Chronicle covering health stories and general news. She began as a reporter in 2023.