A spokesman said the front, preceded by strengthening north to northwest winds, was forecast to move east across the South Island, bringing periods of heavy rain to the West Coast.
A heavy rain warning and watches are now in force.
"In addition, north to northwest winds preceding the front may approach severe gale across parts of the South Island, and strong wind watches are also in force."
He said Southland and Fiordland may be affected until midnight tonight, and the Canterbury High Country about and south of Arthur's Pass, Central Otago and the Queenstown Lakes District many be affected between 2pm today and 3am tomorrow.
"People are advised to keep up to date with the latest forecasts in case any changes are made or further areas are added."
