A cold front is expected to move northeast over the South Island during Thursday and the North Island early Friday.

The northwesterlies ahead of the front, and the westerly change following it are expected to be strong over New Zealand and could reach severe gale for a time in exposed places.

A Strong Wind Warning is already in place for Wellington and southern Wairarapa. A period of northwesterly gales are also expected in Marlborough and Canterbury today.

From Thursday night until Friday morning, west to northwest gales are likely about Northland, Auckland and the Coromandel Peninsula, while westerlies gales are expected about exposed coastal places of Southland and Clutha.

During Friday evening, westerlies behind the front are expected to reach gale in exposed areas of the North Island from Central Hawkes Bay to Wairarapa.

A period of heavy rain in the northwesterly flow ahead of the front is also expected about Fiordland and the Otago headwaters this morning and afternoon.

There is the possibility that the wind and rain may reach warning criteria in these areas. People potentially affected should keep up to date with latest forecasts, and look out for any upgrade of this watch to a full warning.