Winter has arrived for Canterbury with a complex low pressure system that will drive colder southeasterly airflow onto region on Sunday, bringing a significant period of rain, which will fall as snow on higher ground.

Blue Skies Weather & Climate Services forecaster Tony Trewinnard said after a brief break early Monday, another period of rain and snow will arrive during Monday, but with the airflow warming and snow levels rising.

Further cold, cloudy, showery weather is expected through the rest of next week.

He said farmers can expect snow lowering steadily during the day on Sunday to 400m by late in the day, with accumulations of 5-10cm to 400m and 10-20cm above 600m.

After a brief break, a further 5-10cm may fall from mid morning Monday, but snow levels will rise steadily during Monday afternoon with snow turning to rain, and rain clearing most settled snow below 800m. 

A few further light snow flurries are possible above 500m later in the week.

Travellers can expect significant snowfalls on alpine passes on Sunday and Monday, with accumulations of 10-20cm of snow possible by midday on Monday.

However, a change to rain with rapidly rising snow levels should clear much of the settled snow by later on Monday.

Strong southerly winds and heavy swells will affect Cook Strait from Monday through Wednesday and may impact travel. 

Snow may affect inland Southland Otago above 300m on Sunday, but should clear on Monday.

Tresca Forrester, Journey Manager for Waka Kotahi NZ Transport Agency said “don’t be caught out just because it has been a relatively mild start to winter to date, check the weather before you go and be prepared for possible disruption to your journey.

“The first heavy snowfall of winter is forecast to occur during this long weekend although Saturday is looking fine at this stage in many places. We want everyone to stay safe and have a great long weekend so please monitor the forecasts and plan your journeys.”

Waka Kotahi road crews are on standby over the weekend. They will work to clear any snow that arrives and reopen the highways when it is safe to do so.