A well-marked cold front from the Southern Ocean is slowly moving up the South Island with some rain and a big temperature drop behind it.
Some places on Tuesday, like Dunedin, Queenstown, Alexandra and Wanaka, may fail to even reach the teens with highs between 10 and 12 degrees forecast.
The area of heavy rain is moving northwards along the West Coast, says WeatherWatch.co.nz.
"Today the front sweeps over the middle area of South Island, bringing rain to both sides of the Southern Alps.
"From Thursday the main area of rain will move to the North Island. The amount will be not as heavy as that in Fiordland and Westland but may still have localised heavy falls."