Snow and cold winds hitting parts of the South Island have the potential to create blizzard-like conditions, MetService says.
A severe weather warning is in place for Fiordland, Southland and Clutha, with heavy snow up to 40cm deep expected above 100m.
State Highway 94 from Te Anau to Milford Sound is closed because of snow.
Meteorologist John Law said the cold front would move up the country during the week.
"If you're out in those stronger winds and up over the higher ground, if you're caught in those snow showers it's going to reduce your visibility and it's going to make it feel incredibly cold.
"And of course blizzard-like conditions at the tops of the high ground as well."
Snow showers were expected to become heavier and more persistent in ther region from Monday through to Tuesday night. In the 24 hours from 9pm Monday through to 9pm Tuesday MetService said to expect 20-40cm to accumulate above 100m, with 5-15cm at lower levels.
The transport agency (NZTA) is urging drivers in the South Island to be vigilant, with a wintry blast expected to affect roads and main highways.
NZTA journey manager Lee Wright, said people travelling through alpine passes should be prepared as weather can change quickly and it only takes a split second to lose control of a car in bad conditions.
Snow showers are expected over the next three days in the Lindis, Arthur's, and Lewis passes.
It's just two weeks since almost the entire South Island woke up to temperatures below zero degrees.