An El Nino system is forecast to bring ''slightly cooler'' weather across the country this winter - not that southerners may notice.
But be warned, spring in Otago could be ''cold, windy and nasty'', the MetService says.
''That's a typical response, which doesn't mean you're going to get it this time,'' meteorologist Georgina Griffiths said yesterday.
But, ''if you have to bet money on it ... I would say, a cold spring'', Ms Griffiths said.
Following significant climatic changes in the past two weeks, the Australian Bureau of Meteorology has confirmed that El Nino thresholds have been reached in the tropical Pacific for the first time since March 2010.
Climate scientist Prof James Renwick, of Victoria University, said an El Nino system towards the end of the year could be the most notable the country had seen in perhaps a decade.
Ms Griffiths said cold weather which brought hail and snow to Otago last November was not El Nino-related.
''That was a Southern Ocean thing.''
Winter would probably be ''slightly cooler'' nationwide as a result of El Nino weather patterns, but would not be noticeable in Otago, she said.
''Local influences'' would play a larger role in determining the weather.
''At the moment, we have a very active Tasman, which is why it was been really warm.''
- Additional reporting The New Zealand Herald
