Police are warning of black ice on roads across Canterbury after two crashes this morning.
Police said the ice had been reported right across Canterbury this morning and urged drivers not to travel unless absolutely necessary.
Drivers were warned to take "extreme care" on the icy roads after a single-vehicle crash before 8am closed Tunnel Rd in Christchurch and left the car's driver seriously injured.
Earlier, a vehicle smashed through the railings of the Old Waimakariri Bridge on Main North Rd and ended up in a creek. The driver was unscathed but the bridge remained closed as contractors could not inspect it because of ice.
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Cantabrians were among many southerners waking to bone-chilling temperatures as snow and frosts rounded off the first week of winter. They woke to temperatures around -4C, according to MetService.
Tekapo got the worst of it overnight at -6.6C, with Pukaki Airport close behind at -5.9C and Alexandra down to -4.8C, according to MetService.
A cold front is pushing very chilly air up the South Island, with MetService meteorologist Tuporo Masters predicting people in the South would be "in the freezer" overnight with temperatures around -5C.
"That is really severe. So we go severe frost when we see air temperatures minus five. However, the ground temperature might be minus 10."
Heavy snow closed multiple roads on Saturday. State Highway 94 between Hollyford Rd and Chasm remained closed early this morning, as did SH73 between Springfield and Otira. The latter has now reopened.
Snow showers are expected on Arthur's Pass, Lindis Pass, Haast Pass, Crown Range Rd and Milford Rd this morning, and in the afternoon on the Lewis Pass.
Black ice means conditions are still dicey on many roads in the south, especially around Dunedin, Wanaka and the Mackenzie Region.
Severe frosts are also expected in Marlborough through to Otago this morning before a fine day, with a few showers about the Southern Lakes.
From Buller through to Fiordland, including Southland, a few showers will become more frequent with the possibility of hail, according to MetService.
Today is also expected to be colder than Saturday around the North Island, and showery weather is expected for much of the island this morning.
Although the sun is expected to break through this afternoon it may not bring much warmth, as upper North Island temperatures struggle to reach the mid-teens.
Scattered showers are expected in Coromandel, Auckland, Northland, Bay of Plenty, Gisborne and Hawkes Bay before becoming fine.
The rest of the North Island can expect fine weather from earlier in the day, apart from a few light showers sticking around between Manawatu and Taranaki.
Looking further out, forecaster Weatherwatch says the coming week will be drier than normal but rain should return the following week, bringing June's rainfall totals closer to normal for the north of New Zealand.
Showers clearing this morning and fine spells developing. Southwesterlies. High 15C, Low 8C
Showers clearing before dawn and fine spells developing by afternoon. Southwesterlies. High 15C, Low 10C
Fine spells developing. Southwest breezes. High 14C, Low 4C
Fine. A few showers clearing before dawn. Southwesterlies. High 15C, Low 6C
Cloudy periods, and a few showers mainly in the evening. Southwesterlies. High 14C, Low 7C
A few early showers, then becoming fine with southwesterlies easing. High 15C, Low 5C
Cloudy periods and a few showers. Southwesterlies turning westerly in the morning. high 15C, Low 9C
Becoming fine as southerly breezes turn northwesterly this morning. High 12C, Low 7C
Fine. Southwesterlies. High 13C, Low 3C
A frosty start then fine. Northwesterly breezes. High 12C, Low -2C
Fine. Light winds. High 12C, Low 5C