State Highway 1 has reopened following a closure caused by a crash at Palmerston earlier this morning.
The highway was closed after a station wagon rolled near the overbridge by Horse Range Rd about 8.20am, emergency services said.
Few details were available but it is believed there were seven people in the vehicle.
Two were initially described as being in a serious condition and were transferred to Dunedin Hospital by helicopter, a St John spokesperson said.
Two others received moderate injuries, the spokesperson said.
The New Zealand Transport Agency advised of the closure - between Horse Range Rd and Fleming Rd - just after 9am, but said it had reopened around 10am.
The crash occurred on a morning when wintry conditions again made life difficult for motorists in the South.
Several highways were closed this morning but must have now reopened, the exception being State Highway 94 Te Anau-Milford.
There are cautions on several other roads, including SH85 Kyeburn-Palmerston, and SH87 Outram-Middlemarch.
- Check road conditions here
Black ice on the runways caused delays at Queenstown Airport this morning, with at least one flight cancelled. The airport advised via Twitter that flights were now on schedule, but there could be weather-related delays throughout the day.
- Check flight status here
Meteorologist Ciaran Doolin said Balclutha, Dunedin and Oamaru would be hardest hit by a cold front sweeping across the region, after what had been a relatively warm and sunny week for many.
Traffic on the Northern Motorway was reduced to one lane about 8.30pm yesterday after two cars slid into a ditch because of the wintry weather conditions, Senior Sergeant Brian Benn said.
Traffic control was in place for about an hour and the road was opened to two lanes again after grit was applied and backed-up traffic was cleared.
Two minor crashes, in Lumsden and Invercargill, also appeared to be caused by the weather.
No-one was injured in any of the incidents.
Thundery showers were expected in coastal Otago this morning, with the possibility of heavier showers and snow throughout the day.
''It's certainly going to be cold,'' Mr Doolin said.
Snow was expected to continue falling to low levels throughout southern and coastal parts of Otago tomorrow.
Snow showers in Queenstown and Wanaka were expected to clear this morning but return tomorrow.
The cooler weather affecting Otago was expected to gradually clear on Monday.
''The cold air that is responsible for this weather will gradually move off slightly to the north and then to the east.
''Once that's gone, the shower activity should clear,'' he said.
The New Zealand Transport Agency issued a warning for drivers in parts of Otago yesterday.
It advised snow chains were needed for vehicles travelling on State Highway 8 from Omarama to Tarras, and H87 from Middlemarch to Outram.
Haast Pass, on SH6, remained closed overnight because of snow.
NZTA asked drivers to take extra care during the weekend and check its website regularly for road updates.
john.lewis@odt.co.nz/additional reporting John Gibb
