A hot summer in Whanganui according to Niwa’s seasonal outlook

Warm sea and land temperatures are forecast for Whanganui this summer. Photo / Bevan Conley

Whanganui will most likely get a hotter-than-average and wetter summer.

The National Institute of Water and Atmospheric Research’s (Niwa) summer outlook revealed a 60% chance of higher-than-average temperatures for the region and just a 5% chance of it being lower.

Niwa said heavy rainfall totals are 35% likely to be above normal with a 40% chance of being average.

Heavy rainfall events “cannot be ruled out”.

It also predicted average soil moisture levels and river flows (a 40% chance).

The summer climate outlook covers weather probabilities for December, January, and February.

Niwa principal scientist Chris Brandolino said westerly and northwesterly winds are expected through December.

But, according to Brandolino, Whanganui can look forward to a mostly dry month, with wet weather likely to increase through January and February.

“Despite the drier lean at the beginning of summer, when you look at the three-month period in totality, across the west of the North Island, the rainfall is going to be in the normal range and maybe even above normal,” Brandolino said.

The potential increased rainfall aligns with the expected La Nina weather pattern, which maintains warm ocean and land temperatures.

“Warmer-than-average temperatures will certainly be more common than cooler-than-average temperatures. I can say that with high confidence,” Brandolino said.

“Unusually warm, even hot, will be a theme for the summer season.”

The western North Island had the highest sea surface temperature anomalies in the country for 30 days, until November 26, with an increase of 1.04C compared to the 1991-2020 climatological period.

This increased sea surface temperature is expected to continue during December and possibly the whole summer.

“We are already seeing marine heatwave conditions. The water is not only unusually warm, it’s highly unusually warm. It’s an anomaly,” Brandolino said.

Overall, Brandolino said Whanganui was set for an unusually hot summer.

Olivia Reid is a multimedia journalist based in Whanganui.