Several South Island towns are without power as a polar blast sweeps the country

Alpine Energy is reporting outages in South Canterbury towns' including Fairlie where temperatures have been around minus five this morning.

MetService has an orange snowfall warning in place for inland Canterbury from the Rakaia River southwards with up to 18 centimetres of snow forecast in higher elevations.

Snowfall warnings apply today for multiple South Island roads - and for the North Island's Desert Road.

The cold temperatures are expected to hang around today, with many South Island daily highs remaining in the single digits.