Niwa: Whanganui’s summer much warmer than usual, especially in December and January

The average temperature for Whanganui's summer was a whole degree above normal. Photo / Bevan Conley

Whanganui’s summer was a smash hit with temperatures in December and January higher than normal.

National Institute of Water and Atmospheric Research (Niwa) principal scientist Chris Brandolino said temperatures recorded at the Whanganui Airport over the summer revealed an interesting trend.

For the summer season in Whanganui — December 1 to February 29 — the average temperature was a degree above normal compared to the past 30 years.

The average temperature across the summer period was 18.6C.

“That’s pretty meaningful to be a degree warmer than what is typical,” Brandolino said.

“The reason summer was warmer than average was largely, if not entirely, due to December and January. Those two months were unusually warm.”

The highest temperature across the whole of the summer occurred in January and was 30.3C at Whanganui Airport.

In January the mean temperature was 19.5C and that was considered well above average.

“Those daytime temperatures were highly, unusually warm,” Brandolino said.

As well as having above-average temperatures, December had only 76 per cent of the normal amount of rainfall.

February was the coolest month with the mean temperature at 18.1C, which was “spot-on” for what was considered average for the month, he said.

“A lot of the country had more average temperatures in February.”

Brandolino said the reason for February’s coolness may have been the impact of El Nino, which led to more westerly winds.

Whanganui Airport recorded 157mm of rain within the three-month period of summer and that was considered within the near-normal range.

“That’s perhaps on the drier side,” he said.

Normally, Whanganui receives 189mm of rainfall during the summer season.

Across New Zealand it was the ninth-warmest summer on record for the country since 1909.

Eva de Jong is a reporter for the Whanganui Chronicle covering health stories and general news. She began as a reporter in 2023.