Blue Skies Weather and Climate Services has forecast a period of snow for the Canterbury High Country and Plains, as a colder southerly airflow is set to increase tomorrow.

The airflow will shift to a southwesterly direction by tomorrow night, leaving only a few sleety showers on Monday.

Farmers in the region should prepare for rain to develop tomorrow, with snow levels lowering to 300 meters in the morning.

North Canterbury is expected to experience heavy rain and snow, particularly in the afternoon and evening.

In Mid and South Canterbury, snow accumulations are expected to reach 5-10 cm at 300 meters and 10-20 cm above 500 metres.

North Canterbury could see snow accumulations of 10-20 cm above 300 metres.

Brief snowfalls to 200 metres may occur across the region during the evening.

Temperatures are expected to drop significantly throughout the day, with the rain and snow easing to sleety showers by tomorrow night.

Monday may bring light snow flurries at sea level, particularly along the coast and on Banks Peninsula. Temperatures will remain very cold, with strong southwest winds creating significant wind chills.

The weather is expected to clear by Monday night, but there is a risk of heavy frosts inland.

Fine weather is forecast for Tuesday, though widespread heavy frosts are possible that night.

The period from Sunday through Monday night is likely to be particularly challenging for newborn livestock.

Travellers should be aware that snow is likely to impact alpine passes and inland roads above 300 metres later tomorrow.

Some passes may need to close on Sunday night due to the snow.

Inland roads and roads on Banks Peninsula above 200 meters could also be affected by snow during the evening and into Sunday night. Light snow flurries may occur at low levels on Banks Peninsula and the Port Hills on Monday.