It was the same story inland at Waiouru, where the top daytime temperature was 11.1C on August 11, and the coldest daytime temperature was on August 6 - a day straight after a snowstorm - when the temperature never topped 6C.
Waiouru's average minimum air temperature across the month was 5.1C - that's 1.8C above its usual average.
It has now been 31 consecutive months since New Zealand experienced a nationwide average temperature at least 0.5C below its 1981-2010 average temperatures, Niwa said.
However, there were some cold times here during August. Whanganui had the possibility of three frosts, with temperatures dipping below 4C overnight on August 2 and again on August 19 and 20, when clear, still weather followed a cold snap.
In Waiouru the temperature dropped to a chilly -4C on both August 19 and 20.
While parts of the West Coast were drenched with rain during the month, Whanganui only had three days with more than 10mm of rain.
"There were no big, dramatic rainfalls," Kerr said.
On high ground inland, water can fall from the air as snow. The Desert Rd was closed by snow on August 4 and 5, when there were blizzard conditions on Mt Ruapehu. Snow fell again on the mountains of the Central Plateau in the final week of August.
Nationally, the sunniest parts of New Zealand during August were Nelson and Marlborough, with Hawke's Bay and the Bay of Plenty coming next.
There were quite a few windy days, with winds mainly from the southwest. Taranaki had tornadoes on August 12.
