The Desert Road section of SH1 between Waiōuru and Rangipo was closed at 5.50am and remains closed.
Motorists looking to travel through the region via SH1 will have to detour through SH47 or SH46 to National Park, SH4 to the Tohunga Junction and SH49 to Waiouru before rejoining SH1.
MetService issued a road snowfall warning for Desert Rd, with snow forecasted to fall between 3am and 3pm Wednesday.
Police advised motorists to plan accordingly and follow diversions and MetService reminded those on the roads to switch their headlights on, increase following distance and be prepared for unexpected hazards.