Climate scientists say the Pacific could be battered by up to 10 tropical cyclones in the next six months.
NIWA has released its outlook for the upcoming cyclone season, from November to April next year.
NIWA predicts there will be between eight to 10 tropical cyclones in the Southwest Pacific during the season.
It says between five and six of those storms could be Category 3 or higher - a Category 5 being the most severe on the scale.
NIWA said they could occur anywhere across the Southwest Pacific - and advised communities to be vigilant and follow forecast information.
It said, on average, at least one ex-tropical cyclone passed within 550 kilometres of New Zealand every year - and if that happened there was a greater chance it would pass east of Auckland and the North Island.
Earlier this year, the country was hit by severe flooding, slips and power outages caused by the remnants of Cyclone Cook and Cyclone Debbie.
The peak period for cyclones in the Pacific is usually from January to March.
The Fiji Met Service said tropical cyclone risk was expected to be normal for Fiji, Southern Vanuatu, New Caledonia and Wallis and Futuna.
It said a reduced risk was expected for Solomon Islands, Tokelau, Samoa, Tonga, Niue and the Cook Islands, while cyclone activity was unlikely for Kiribati and the Marquesas this season.