UPDATED 5.29pm: Plummeting temperatures across the South Island could spell more snow on the way.

Severe frosts mixed with strong winds bringing a strong wind chill factor could turn rain to snow this afternoon and overnight.

MetService has issued a severe weather watch for parts of Southland, Otago, Fiordland and Canterbury.

Meteorologist Emma Blades acknowledges the southern residents are in for a few flurries.

"We're talking snow accumulations above 200-300 metres, at the moment it's only a watch but it could approach warning amounts."

"You might see a little bit of snow in Christchurch even."

With towns like Timaru expected to have minus-nine degrees overnight, freezing temperatures and biting winds will certainly bring severe frost.

Weather commentator Richard Green reports it's going to be a chilly night.

"Snow is expected to develop late this evening in the hilly areas of Christchurch and a little earlier for Dunedin and South Otago. Very cold southerly winds are accompanying these very wintry conditions expected to last throughout much of Monday morning."

Green adds flurries of fresh snow could fall to low levels overnight.

"Temperatures, even thought hey're going to remain in single figures, will feel much colder that that with the biting southerly and some of the snow, even though it's coastal for Canterbury, could reach as far in-land as Darfield just topping up what they saw a few days ago."

Road warnings are also in place across the South Island. Emma Blades said snow showers are expected to affect the higher roads.

The Arthur's, Lindis and Porters Pass could all be icy.