And Weatherwatch.co.nz says that although it's not completely clear if it will affect the country, previous cyclones have been deadly because of dangerous rips and large waves.
The tropical cyclone is due to form around Fiji or Tonga and, according to computer modellings, will intensify as it drifts west, possibly becoming "severe".
It's also claiming that it will "be a much bigger storm than [Cyclone] Fehi", which struck the Pacific last week.
Niwa has dubbed the cyclone Gita and says there's a "moderate" chance of the cyclone forming over Fiji in the the next three days.
It follows from their earlier tweet in which they noticed a "disturbance" occurring in the tropics, east of Vanuatu and south of Fiji.
WeatherMap.co.nz uses American models for its forecasts, and they show a direct hit to Northland and Auckland.
However, the European models (ECMWF) show it moving into the Tasman Sea and in a position that could affect either island of New Zealand.
"It's still early to know if this cyclone will directly affect us," says Weatherwatch.co.nz.
However, MetService says the weather event was still a week away and a bit too far off to be precise.