Hurricane winds and extreme amounts of rain have already reached the country, and the situation is expected to get even worse in the coming 24 hours.
Hundreds of flights and train departures have been canceled and at least 46,000 households have lost power, the BBC reports.
The storm has been named Gabrielle by the weather service, and on Monday evening Swedish time, its center is out at sea, about 200 kilometers northeast of Auckland, on the North Island.
The country's Prime Minister Chris Hipkins is stranded in the city and unable to get to the capital Wellington due to canceled flights.
In the near future, Gabrielle is expected to cause storm waves, extensive flooding and landslides mainly on the North Island.
Schools are closed and residents are asked to stay indoors.
Close to two million people in nine regions are affected by the state of emergency, which is only the third in the island nation's modern history.
The article is updated