Weather: 'Autumnal chill' coming as New Zealand hit by 'southerly air flows'

New Zealand is in for a proper "autumnal chill" over the next week as cold southerly air flows bring temperature drops.

"Cool southerly winds have set in over the entire country, following the movement of a cold front away from the North Island earlier today," MetService says.

"High pressure becomes firmly established over much of the South Island overnight tonight and into Wednesday, bringing clear skies, light winds and the potential of frosts for inland valleys and basins."

The drop in temperatures brings with it a medium to high risk for frost in the interior of the South Island on Tuesday night.

"Protect your plants and keep in mind your four-legged friends, too," NIWA says.

Wednesday morning temperatures in the South Island are expected to be as low as 2degC in Alexandra, 3degC in Queenstown and 4degC in Wanaka and Timaru.

In the North Island, Waiouru will sink as low as 3degC and Masterton will drop to 4degC.

After this, Weather Watch says another cold front on Thursday and Friday will head north, bringing another surge of showers and cooler air to southern and eastern areas.