MetService forecaster Tuporo Marsters said to expect snow on Friday after a high of 20degC on Wednesday and Thursday.
"There's a cold outbreak with snow down to low levels [on Friday].
"We're saying about 300m for the Deep South at this stage, including Dunedin, and possibly even lower as the day goes on."
Friday was expected to reach a high of just 8degC and a low of 3degC.
Mr Marsters explained that the change in weather would be felt across the country, but it would be especially bad in Dunedin.
"The reason it's going cold on Friday is because there's cold snow showers and cold air coming from Antarctica, straight from the ice.
"With any cold outbreak, it's the Deep South that gets affected first."
The cold weather will come after a relatively warm week, with occasional rain expected for today and Thursday.
"We’ve got a bit of a warm morning on Thursday with 20degC, but by nightfall it plummets down to 3degC."
"So that's a very unusual change."
The wind would pick up on Friday, turning into westerly gales.
Southland is also expected to feel the cold southerlies.
On Saturday the temperatures should climb back up as the cold air moves eastward.
