Weather: 'Autumnal chill' to bring 10C temperature drop to parts of New Zealand

A cold change is on the way for parts of the South Island as southerly winds bring an "autumnal feel".

MetService says parts of the South Island's east coast could drop 10C on Tuesday evening when that southerly hits.

"A front is just coming through Dunedin - temperatures dropping from 22C to 16C in the last 60 mins," said a post on the forecaster's Twitter page early Tuesday afternoon.

NIWA says the cool change will bring a "proper autumnal chill".

"The humidity will also decrease," the forecaster said on Facebook.

A heavy rain warning is in place for Westland south of Otira. On the east coast of the South Island, Dunedin's temperature will plummet to 15C on Wednesday after reaching 22C on Tuesday, while Christchurch's temperature will almost be cut in half - dropping to 16C down from 30C on Tuesday.

"Wednesday will be colder than average in a number of southern places as a Southern Ocean southerly wipes away the warmer sub-tropical northerly," WeatherWatch says.

"The cooler change also moves into the lower North Island but highs will still make the late teens."