Some 46,000 homes have lost power as Cyclone Gabrielle lashes the north of New Zealand.
Authorities have issued warnings of heavy rain and winds, and hundreds of flights have been cancelled.
Some areas have declared a state of emergency, as Gabrielle nears the North Island.
It comes weeks after Auckland and surrounding areas were hit by record rainfall that sparked floods and killed four people.
“Extreme weather event has come on the back of extreme weather event,” said New Zealand Prime Minister Chris Hipkins, who announced a NZ$11.5m (£6m; US$7.3m) aid package.
“Things are likely to get worse before they get better.”
Emergency management minister Kieran McAnulty told a media briefing on Monday that the government is considering declaring a national state of emergency for only the third time in the country’s history.
A state of emergency has already been declared in five northern regions including Auckland. The declaration gives local authorities greater power to respond to dangerous situations and allows them to restrict travel and provide aid.
New Zealand’s meteorological agency, Metservice, said Whangarei, a city north of Auckland, had received 100.5mm (4in) of rain in the past 12 hours.
Mr McAnulty added that Monday would be a “critical day” due to the “highly dangerous” combination of high winds and heavy rain. Winds of up to 140km/h (87mph) battered the Northland region, while Auckland Harbour Bridge was rocked by gusts of 110km/h.
He warned that it could take days to restore the power grid as the bad weather made it “unsafe” to work on the network.