Wednesday was Whanganui's the warmest December since 2012. Photo / Bevan Conley
Whanganui has recorded its second warmest December day since records began in 1978.
Measured at Whanganui Airport, temperatures soared to 29.3C, just 0.4C lower than the highest ever.
MetService meteorologist Paul Ngamanu said the warm weather had a bit to do with where Whanganui was positioned.
"We've had this warm, humid air mass over the country for a few days and that is helping bring those temperatures up.
"What is so significant about Whanganui is where it is positioned, you have this 'Foehn effect', which is similar to the warm temperatures Canterbury gets."
A Foehn wind is a warm, gusty wind that periodically descends the slopes of nearby mountains and hills.
"It is caused by the air moving over the high ground and warming up as it comes down over the lower ground. What is happening as it moves from the Bay of Plenty and through the high country of the North Island through the Whanganui region.
"Those temperatures aren't just in Whanganui, but through the Manawatu, Kapiti are experiencing warm temperatures and even Wellington."
A severe weather warning has been issued to the lower central North Island as seen below.
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