Motorists have been warned to expect waves of up to 3.5m along State Highway 1 as strong winds batter Canterbury.
Metservice has issued a strong wind watch for the Canterbury High Country and the ranges of Marlborough, south of Ward, from 8am to 9pm on Friday.
On Thursday, it said the strong westerlies are expected to be widespread.
"Watches for strong winds are in place for areas of particular concern, though more may join the ranks as the weekend progresses."
Motorists travelling on State Highway 1 on the Kaikōura Coast should watch for big waves at Ohau Point north of the town from Friday afternoon until Saturday.
The waves were forecast to reach up to 3.5m and traffic control will be in place if needed.
Waka Kotahi NZTA said crews will be monitoring roads and applying grit or an anti-icing compound if necessary.
A road snowfall warning is also in place for Porters Pass (SH73) from 5am-8am on Saturday.
"Snow is expected to briefly affect the road; 1-2cm of snow may settle above 500 metres," Metservice says.
Heavy rain is expected to hit the South Island's west coast from Sunday.
A strong west-to-southwest flow meant that snow would also spread and drop to lower levels in much of inland Otago and Southland tomorrow, possibly moving as far east as the hills around Dunedin.
While it was not expected to cause any disruption, it would bring very cold temperatures.
"Along with the wind, it’s going to be rainy and temperatures will be dropping, so it’s going to feel pretty grim."
More "fast-moving fronts" were expected to travel up the country into the second week of school holidays.
On Monday, severe northwest gales followed by severe southwest gales are likely for Southland, Stewart Island and Clutha.
It was also likely severe southwest gales would affect Dunedin and North Otago.
In the North Island, a strong wind watch is in place for Northland, 6am to 3pm Saturday, Auckland, Great Barrier Island and Coromandel Peninsula from 4am to midnight Saturday, and until 6am on Saturday for Tararua District and Hawke's Bay south of Hastings.
"Northwesterly winds are expected to tip southwest around midday, marking Auckland's first strong southwesterly event since early August. Along with the wind, it's going to be rainy and temperatures will be dropping, so it's going to feel pretty grim."
-Additional reporting RNZ and John Lewis, ODT
