Gale-force winds have also been hammering the lower South Island this morning as a front moves over the country, bringing a cold change that is likely to dump snow to sea level later today.
The MetService has issued severe weather warnings for much of the lower South Island, with strong wind warnings for Southland, Otago and Canterbury.
Heavy snow warnings are in place for Fiordland, Southland and Clutha, while a heavy rain warning is in place for the ranges of Westland south of Otira.
Inspector Olaf Jensen of Southland police said gale-force winds had brought trees down and caused limited power disruption in some areas of the region.
Roads remained open but motorists were advised to to exercise "extreme care" on Southland roads.
Police and Emergency Management Southland were monitoring the situation.
The MetService said strong westerly and northwesterly winds were gusting up to 160km/h as the front moved over the South Island.
The front would be followed by a cold change that would see temperatures plummet, bringing snow to low levels in warning areas.
MetService severe weather forecaster Leigh Matheson said the strongest winds this morning were in the Foveaux Strait, Stewart Island and Southland.
The Foveaux Strait was being battered by 100km/h winds, gusting up to 160km/h, while 60km/h gales in Invercargill were gusting up to 120km/h.
Strong winds were also hammering Otago, with 50km/h northwesterly winds in Dunedin gusting up to 80km/h.
Ms Matheson said the gales should ease this morning as the front moved over the country.
"Temperatures are expected to drop significantly from later this morning into this afternoon, so snow will gradually lower from this afternoon into this evening," she said.
In Fiordland, snow below 300m was expected from this afternoon, becoming heavy this evening. Heavy snow would follow in Southland and Clutha from about midnight.
"In all of those areas, we're expecting snow to near sea level. But the significant amounts, or the large amounts, will probably be above about 300m," Ms Matheson said.
Snow was likely to push further north tomorrow, with southern parts of Central Otago and Dunedin expected to see some snow to low levels, but not in large amounts.
Heavy rain was falling in Westland this morning, with 30-40mm of rainfall in the ranges since midnight. The rain was not expected to ease until this afternoon.
