A heavy snow watch is in place for Central from 2pm on Saturday July 1 until 5am Monday July 3, so stock your firewood baskets, and keep on top of road information if you are travelling.

The MetService said snow is expected to fall down to 100 metres at times in Otago, south of the line from Queenstown to Alexandra and Mosgiel, and for Southland and Stewart Island.

Periods of heavy snow are possible above 300 metres where accumulations may approach warning criteria.

MetService meteorologist Alain Baillie said this will mean snow to very low levels in the far south, with heavy snow possible in elevated areas, including the resorts near Queenstown, with the town itself also likely to get snow.

MetService seven day forecast for Alexandra shows temperatures dropping to below zero

Snow could also fall to 200 metres around Dunedin, and 300 metres over Banks Peninsula from Saturday night, which will affect many roads. 

Drivers are advised to watch out for fog, dip their lights, and drive slower to suit the conditions to avoid rolling or sliding off the road or into another vehicle. 

Those travelling about the South Island, particularly if you're travelling through passes, should check the Central App reports section for up to date weather and road information.