A police spokeswoman said four cars crashed in Heriot Row from 8.20am.
The crashes were between London and Constitution St.
"The road is slippery and cars are sliding down the hill on the frost, the drivers of the four cars have no injuries.''
Three of the four vehicles could be drivable but police advised them to wait, she said.
Authorities would assess reopening the road later this afternoon, she said.
Police blocked both ends of Heriot Row to stop more vehicles crashing.
The Dunedin City Council this morning advised of treacherous conditions owing to widespread frost, and urged motorists to take extreme care on roads around the city.
Inland, the Queenstown Lakes District Council says ice and grit have been reported down across the length of SH6 from Wanaka through the Kawarau Gorge, past Frankton to Kingston.
There is also ice and grit on the Crown Range, particularly the Wanaka side.
The Central Otago District Council advises that all roads are open except for Danseys Pass, but ice and grit are widespread in the region.
MetService shows a cold start in the South, Dunedin Airport recording a temperature of -4degC at 7.30am.
Other cold spots included Queenstown on -2C, Invercargill on -1.5C and Ranfurly, which fell to -3.7C.
MetService meteorologist Josh Griffin said temperatures will be similar tonight.
Auckland was at 8.5C overnight and Hamilton dropped to 2.8C.
Rotorua hit 5C, Wellington was a bit warmer on 7C and Christchurch dropped to 4C.
Meanwhile, fog is lingering at Christchurch and Dunedin airports this morning.
Fog caused flights to be cancelled coming into Dunedin yesterday and it has stuck around this morning.
Mr Griffin said the fog should clear in both spots by 11am.
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Comments
In '93, ODT said to wear socks on the outside of footwear. A different time. Now, people are worried they'll look 'barmy', er, non normative.
From Arthur Street I still see people wearing socks on the outside. Great idea! Could be a new fashion.