"Winter-like temperatures" will descend upon the South Island next week as a blustery southerly drags up cold air from the Southern Ocean.
A NIWA graphic video shows an ice-cold claw of cold weather stretching out from near Antarctica towards New Zealand.
"Check out the source region of the air mass coming for the South Island on Tuesday," it says, along with a penguin emoji.
"Winter-like temperatures are expected in the South Island, particularly in the deep south and about the interior.
"The North Island will have brisk conditions thanks to the wind chill factor."
MetService warns this southerly change will bring rain to southern and western areas, with a low confidence rainfall amounts will reach warning criteria about Mount Taranaki, the Tararua Range, the ranges of Buller and Westland, and Fiordland.
Some of this rain will fall as snow for some thanks to this cold airmass. Snow is expected to fall to "significantly low levels" on Tuesday morning for Fiordland, Southland, Clutha, Otago and Southern Lakes.
"There has been a Road Snowfall Warning issued for the Crown Range Road and Milford Road in association with this cold change. These become valid from Monday evening," MetService states.
Crown Range Road
Valid: 4 hours from 8:00pm Monday to 12:00am Tuesday
Forecast: Snow showers are likely from Monday evening, and 1 to 2cm of snow may settle near the summit of the road from 8pm to midnight Monday. Please note, more snow is expected on Tuesday.
Milford Road (SH94)
Valid: 7 hours from 5:00pm Monday to 12:00am Tuesday
Forecast: Snow showers are likely from late Monday afternoon, and 2 to 4cm of snow may settle near the tunnel, with lesser amounts to 700 metres. Please note, a significant amount of snow is expected on Tuesday.
On Tuesday, there is a moderate confidence of severe west to southwest gales about exposed coastal parts of Southland and Otago.
There is also moderate confidence of severe west to northwest gales in exposed parts of Wellington and Wairarapa including the Tararua District, and Hawke's Bay south of Napier. This threat for central Hawke's Bay continues into Wednesday.
