More grim news for Canterbury farmers as the region braces itself for freezing weather this weekend.

Federated Farmers has issued a warning to all farmers, advising them to ensure their stock have enough feed to last up three days.

Snow is expected to fall to around sea level, and about 50 centimetres is likely to accumulate in parts of the Port Hills.

Forecasters are predicting the nasty weather will set in on Friday night, and continue right through till Monday.

Federated Farmers adverse events spokesperson Katie Milne warns that all farmers will be impacted one way or another especially those with young lambs.

"There are some lambs on the ground and ewes in the middle of lambing now, so those guys will also be taking notice and trying to make sure they've got appropriate shelter for those ewes."

She said power outages should be expected, and farmers should ensure they have adequate supplies to react in any situation.

Blue Skies forecaster Tony Trewinnard has cautions that the cold snap on Friday night could bring snow to sea level, with a considerable dusting on the hills.

He said that the cold weather won't come in a single blast, but will accumulate over the course of three days.

"There is no suggestion in the data we've got of really heavy falls on any short time period, but when you accumulate snow steadily over three days, you could easily be looking at perhaps 30, 40 or even 50 centermetres of snow."

"It does look as though the winds will stay southerly and very cold, on shore, onto Canterbury from Saturday through Sunday, and quite possibly next Monday as well."