"Please take extra care, especially for high-sided vehicles and motorcycles," the transport agency said.
Relatively settled weather is forecast around Aotearoa for Sunday but could turn come Monday.
MetService has issued severe weather watches and warnings of snow, rain and wind for the beginning of the week.
Road snowfall warnings are in force overnight for the Lewis Pass SH7, Arthur's Pass SH73, and Porters Pass SH73, with MetService expecting 20cm to 30cm of snow to settle in places above 800m.
Snow is expected to affect the roads from Saturday afternoon to the early hours of Sunday.
MetService meteorologist Alwyn Bakker said, "although the ski fields will see a welcome top-up just before the school holidays, the trick will be finding a settled day to enjoy the snow".
A severe gale warning for Fiordland forecasts southeasterlies up to 120km/h in exposed places overnight, and Westland south of Hokitika may get severe gales.
For the start of the school holidays, heavy rain is forecast until Tuesday for the Coromandel, Bay of Plenty and Gisborne north of Tologa Bay.
From late Monday into Tuesday, a low is forecast to move southwards to the west of the North Island directing a strong and moist east to northeast flow across the Island.
"With a low moving in, and fronts approaching from the south and north, all bringing rain, we've got a pretty active run of days ahead of us," Bakker said.