Emergency Management Canterbury has issued an emergency alert to residents of Christchurch and Banks Peninsula as MetService forecasts damaging wind gusts of up to 140km/h.
About 5000 homes in Canterbury are without power as high winds hammer the region, and Air New Zealand has cancelled more than 20 flights.
The MetService alert said people should take care while driving as conditions would be hazardous.
"These winds may produce widespread damage, especially to trees, powerlines, and could lift roofs," it said.
"There may be road closures and power outages."
Danger from flying debris or falling trees was also a concern and anyone who had had fires or burn-offs should monitor them carefully, it said.
Fire and Emergency said crews were responding to a "surge" in 111 calls in Canterbury.
By 1.45pm, FENZ said crews were responding to more than 25 calls about lifting roofs, fallen trees and downed powerlines from Leeston to Rangiora.
"Crews are also responding to six vegetation fires from Ashburton to Ashley, fanned by the wind.
"In central Christchurch, crews were called to assist people in a car that was hit by a falling tree."
FENZ said people should not travel unless necessary, tie down any loose items and make sure any previous fires have been put out properly.
"No new fires should be lit at this time. Always call 111 immediately if life or property is at risk."
Air New Zealand has cancelled 21 flights as strong winds batter parts of the country.
The national carrier said most of the flight disruptions are in and out of Christchurch.
Passengers are being told to keep an eye on the Air New Zealand website for updates.
MetService has issued red level wind warnings for the Canterbury High Country and the Canterbury Plains, and for Christchurch including Banks Peninsula.
For the High Country, there could be gusts of up to 150km/h, it said.
The winds were expected to ease late on Saturday afternoon but MetService said another period of severe gales were expected from Sunday morning.
There were also orange wind warnings for Wellington and Wairarapa and Marlborough.
MetService said severe winds were expected to produce widespread damage, especially to trees and powerlines and could lift roofs.
Transport and power networks were likely to be significantly impacted, with road closures and power outages, it said.
Meanwhile, the Canterbury High Country also faces a heavy rain warning, as does Westland.
MetService meteorologist Alwyn Bakker recommended people in the affected areas stay inside, and if they did go out to avoid driving a high-sided vehicle or motorbike if possible.
Orange heavy rain warnings are also in place for Westland, South of Otira, and for the headwaters of the Canterbury lakes and rivers south of Arthur's Pass until 3pm.