The MetService is urging farmers to prepare for possible snow over much of Otago and Southland this week.
Tomorrow, a cold front is forecast to hit the far south of New Zealand from the southwest, before moving northwards across the South Island during Wednesday.
MetService meteorologist William Nepe said there was "low confidence" the front would deliver a period of heavy snow above 500m in southern and eastern parts of the South Island on Wednesday, from southern Fiordland and Southland through to eastern Marlborough.
"Snow is possible to lower levels, as well, in some places during this time.
"It's not to say snow won't fall to 400m or 300m.
"I think it's quite likely there will be snow. The question is, how low will it get and how much will fall.
"Because it's still a few days away, there is still uncertainty about that. We'll be keeping an eye on this system.
"But at this stage, it's unlikely there will be any snow in coastal areas like Dunedin."
He said later on Thursday, a narrow ridge was expected to spread over New Zealand, then a trough would move across the country from the west on Friday.
"This trough delivers another period of snow to southern Fiordland, Southland and Clutha, with low confidence of heavy snow falling above 500 metres in these areas on Friday."
He said there was also "moderate confidence" the weather pattern would bring cold and severe west-to-southwest gales along coastal Southland and Otago.
Mr Nepe urged farmers to be prepared, by moving stock to lower, more sheltered areas.
He also asked drivers to be wary of passes and roads in higher areas around the region.