It's a chilly start as a polar winter blast rips its way through the country.

Snow fell across the country overnight, with 2 to 5cm of the white stuff forecast to settle on the Desert Road above 800m from 5pm on Wednesday through to midday today.

The NZTA says overnight conditions have improved and the Desert Road remains open.

'Please continue to take extra care on all roads around the Tongariro National Park, and between Napier and Taupo, especially this morning.”

The colder temperatures are expected to hang around for a while, as today's southerly change marks the start of a different weather pattern, says the MetService.

'We're in for southwesterlies until at least Monday, with a couple of stronger and colder bursts in store.

'What does this mean for your weather?

'In general, expect cold, showery and windy days. Those stronger bursts bring some more snow to higher ground. Also, those near the coast will notice some larger swells.”