"By midnight we can see it's starting to squeeze onto the North Island as well," he said.
In the North Island, it will be a mostly fine day on Saturday but things are expected to take a turn in the afternoon with cloud and wind increasing in central areas.
On Sunday, many parts of the island could see some heavy rain and strong gales including Auckland, Wellington, Whangārei and New Plymouth.
The cold front comes off the back of a relatively mild week across the country.
Isolated showers are expected in parts of the North Island today but by midday, the rain should have faded with the wind dying down bringing "pretty pleasant" weather for the afternoon and evening.
Napier was the warmest spot in the country at 9am with 21.8C. Auckland was sitting on 14.5C and Wellington 15C.
It should be a sunny day for most of the South Island, with higher temperatures in the afternoon as a northwest flow starts to kick into gear, Hines said.
Christchurch and Blenheim were sitting on 17C at about 9am, with Nelson on 16C.
Severe weather warnings
Orange heavy rain warnings are in place for the Westland ranges and Fiordland as well as the Canterbury and Otago lakes and rivers south of Arthus Pass. Heavy rain watches are in place for the ranges of Buller and Westland.
Orange strong wind warnings are in place for the Canterbury high country, central Otago, Clutha, Dunedin and north Otago as well as Southland and Fiordland.
Strong wind watches are in place for Wellington, Christchurch, the Canterbury plains, and Marlborough.
Metservice says gusts could reach up to 130/kmh in some places.
