The El Nino weather system that has seen droughts around parts of the world has now come to an end.
WeatherWatch head analyst Philip Duncan said sea surface temperatures near the equator have dropped to below the El Nino threshold - meaning New Zealand is due to see a neutral winter.
"Neutral winters create more chaos in our weather patterns, whereas El Nino and La Nina tend to have more predictable patterns.
• Mixed bag of weather for first day of winter
"In a neutral winter, anything can happen - everything gets chucked at us from all directions."
Mr Duncan said this winter may bring on some extreme conditions similar to those seen in 2011, when a snow storm in mid-August saw snow falling in the Auckland CBD for the first time in decades.
The event came after record-breaking warm temperatures months before, Mr Duncan said.
"We aren't saying that once in a 30-year event will happen again, but we are saying we have the similar chaotic weather pattern this year."
Meanwhile, this morning was the coldest morning recorded in Auckland this year, with temperatures hitting 7C at Auckland Airport at 7am.
MetService meteorologist Ciaran Doolin said the whole country would be feeling the cold snap today.
"It's not going to be a very warm day, to be frank."
Auckland: Happy first day of winter! Looking good this morning; a few showers move in later. ^GG pic.twitter.com/CxS37LACTS— MetService (@MetService) May 31, 2016
The warmest place in New Zealand looks to be Whangarei, which has a forecast high of 16C.
While Cromwell, in central Otago, will take the gong for being the coldest place today, with a temperature high of 6C.