Drivers are warned to pay extra attention to potential road debris, but Fiordland, Buller Ranges and Tararua Ranges should expect the most rainfall.
Rain is set to sweep from the Southern Ocean up to the South Island on Friday and carry on to the North Island between Saturday and Monday.
Cold temperatures and rain, heavy at times, are expected to hit southern and eastern areas of the country.
Auckland will feel a few showers — some heavy — on tomorrow morning, continuing throughout the day and into the evening. The heavy rain continues on Sunday, easing to showers on Monday.
It's a similar story in Hamilton, where rain develops tomorrow morning and carries on into Sunday, before easing in the evening. New Plymouth, Tauranga and Napier are all set for occasional rain.
Wellington will also experience rain, with southerlies becoming strong on Sunday.
The upper South Island will have scattered showers. Light winds and rain will clear in Nelson on Sunday. Blenheim will have periods of rain with south easterlies developing.
The east coast of the South Island will remain fine tomorrow morning, before rain and showers hit on Sunday in Christchurch. Dunedin will be mostly fine tomorrow before showers clear on Sunday afternoon.
Greymouth will be mostly fine on Saturday with cloud increasing. Overnight showers begin to clear and an overnight temperature of 6C is expected.
Invercargill will feel the brunt of the cold front, with Sunday set for just 12C and an overnight low of 1C.