Heavy fog has stopped some flights in and out of Christchurch Airport tonight.

The Christchurch International Airport released an alert just before 9pm tonight, warning passengers to check with their airline for updates.

The airport's website shows a number of scheduled domestic flights have been affected.

A flight from Blenheim, four from Auckland and two from Wellington - which were all due to land in Christchurch tonight have been cancelled due to the conditions.

A Jetstar flight from Auckland, scheduled to touch down just before 1am has been delayed.

Meanwhile there's a severe weather watch issued by MetService for most of the North island from Auckland south, and for the Southern Lakes.

Heavy rain is expected in the west of the South Island and in central New Zealand, with northwest gales across much of the country tomorrow.

An active front is forecast to move eastwards across the South Island tomorrow and across the North Island early Sunday, preceded by a very strong and moist north to northwest flow and followed by disturbed westerlies.

MetService says it's likely to be a significant event, with potentially damaging winds across much of the country, but especially the lower North Island.

A warning for severe gale northwesterlies is in force for Fiordland, Southland west of Mossburn, Wairarapa, Wellington, the Marlborough Sounds, Taranaki, Taihape, Wanganui Manawatu and Horowhenua Kapiti Coast.