Pacific Island nations - including New Zealand - face a larger cyclone risk this season, due to the strong El Nino effect.
The National Institute of Weather and Atmospheric Research (NIWA) said more cyclone activity was expected across the southwest Pacific between November and April.
NIWA forecaster Chris Brandolino said the warm waters of El Nino were fuel for cyclones and the outlook was based on previous years with similar conditions.
"It's guidance, it's not gospel, it's not a guarantee, but certainly people, especially in the Pacific Islands, want to be vigilant."
Mr Brandolino said New Zealand normally got at least one ex-tropical cyclone a year passing but there could be more this season.