Flying debris and trees and branches falling across roads could make it unsafe to be outside if predicted severe northwest gales hit Otago, Southland and Canterbury today.
Meanwhile a cold southwest airstream is expected to pass over the South Island overnight and tomorrow, bringing snowfalls down as far 300m in the south and east of the island.
The Otago lakes district, inland Southland, especially near the Southern Alps, and the Canterbury high country were expected to be hit by up to 130km/h winds before winds eased tonight, MetService said.
Fiordland was also expected to experience 200mm-250mm of rain, with the most intense falls of 20mm-30mm an hour. Rain was also expected in Southland and Otago.
Emergency Management Southland urged residents to check all property was secure.
"Take your outdoor furniture inside and check for loose roofing iron or tiles," manager Neil Cruickshank said.
It was also a good idea for householders to check they had torches and spare batteries, and a battery-powered radio in case of power cuts.
"If the gales develop at the strength MetService is forecasting, it will be dangerous to be outside, with flying debris in the air and trees or branches falling across roads. Be prepared to delay travel plans [this] morning if the winds are still dangerous."
Organisers of the Tour of Southland cycling race had been alerted to the severe weather warning.
MetService spokesman Dan Corbett said the strong winds and rain would slowly clear from the south today.
"The southerly makes its way across much of the country on Saturday,reaching the north of the North Island on Sunday," Mr Corbett said. "It's a pretty cold change for the time of year, with snow possibly falling down to around 300 metres in Southland, Otago and Canterbury. After recent mild weather, it may come as a bit of a shock."
Heavier falls are possible above 500 metres where amounts could approach 10cm.
Light snow shows are possible overnight on Lindis Pass and Milford Road overnight, and Lewis, Arthurs and Porters passes tomorrow morning.
The southwest winds should be fresh or strong for a short while after the change and wind chill may be significant for stock for a few hours. Winds should ease and the rain and snow clear during the afternoon in most areas but may continue into the evening over the north Canterbury high country.
On Sunday, there would be more fine dry spells and just a few showers, Mr Corbett said.
The cooler southwest flow would still be around on Monday, Guy Fawkes Day, and showers are possible in eastern parts of the country.
- additional reporting Herald Online