MetService meteorologist Alain Baillie said Omarama recorded the coolest temperature, -6degC at 8am.
"There were some seriously chilly temperatures in the region."
Dunedin Airport dropped to -3.5degC and had associated thick fog, which caused some major disruptions to flights.
Three inbound and three outbound flights had to be cancelled yesterday, and several others were delayed.
Last night, as more fog rolled in, the airport said all flights into Dunedin in the evening had been cancelled.
As a result, today’s 6.05am flight to Christchurch and 6.25am flight to Wellington were cancelled as aircraft were unable to land last night.All other flights were expected to go ahead as scheduled, the airport said.
The fog was created when warm, moist air met snow or cool moisture on the ground. It caused the dew point to rise, creating high humidity which forms fog.
While there were reports of black ice on some roads, a police spokeswoman said there were no reports of any major ice or fog-related crashes around the region.
Mr Baillie said the forecast was for more clear skies over the southern region for the next few days, so people could expect more morning frosts and possible fog.
Alexandra was expected to drop to -5degC this morning and tomorrow, and many other parts of the region could drop to -2degC.
He urged drivers to take care on the roads because black ice could form when temperatures were well below zero like this.
Waka Kotahi NZ Transport Agency Otago and Southland journey manager Nicole Felts said contractors were out on highways applying grit and de-icing agents, as well as snow ploughing if necessary.
