A heavy rain warning was currently in place for Fiordland, Westland and the Otago and Canterbury Headwaters, and a severe gale warning was in force for Southland, Otago and Canterbury.
A severe weather watch for strong winds was also in place for areas of Marlborough, Wellington and Wairarapa.
Strong northerly winds were already battering the capital this morning, and these were expected to strengthen even further this evening and through to Wednesday afternoon.
Severe gales would batter inland areas from Canterbury to Southland this morning, however they would be easing late tonight as the front moved north, MetService said.
The front was expected to reach the North Island on Wednesday, MetService said.
Meanwhile, further north, heavy fog was lying over Auckland this morning.
The fog was expected to clear later today, making way for fine weather, light winds and a high of 17C.
MetService said the front would move away to the east on Thursday, leaving a colder southwest flow with showers.
Today's forecast:
Whangarei: Areas of morning fog otherwise fine. Light winds. High 17C Low 9C
Auckland: Morning fog, then fine. Odd shower in west. Light winds. High 17C Low 11C
Hamilton: Mostly cloudy, possible morning fog. Light winds. High 16C Low 9C
Tauranga: Cloudy at times. Light winds. High 17C Low 12C
Wellington: Cloudy periods, drizzle develops. Strong northerly, gale later. High 15C Low 14C
Christchurch: High cloud. Northwest winds, strong and gusty at times. High 17C Low 9C