Winter's kicking it up a notch - with frosty temperatures in most parts this weekend

An orange heavy snow warning's in effect overnight for Inland Canterbury, from Rakaia River southwards.

Snowfall warnings apply today and tomorrow for multiple South Island roads - and from 5am tomorrow for the North Island's Desert Road.

MetService metereologist John Law says snow could settle above 500 metres in southern parts of Canterbury and northern parts of Otago.

He says that will impact the higher South Island passes through tonight - and even up to the Desert Road tomorrow.