MetService says snow showers are expected to lower to 300 metres today in the South Island as the sub-tropical lows leaves the country with a wintry flick.

Snow is forecast to become widespread and heavy above about 400 metres overnight tonight.

MetService says in the 12 to 15 hours from 9pm Thursday, expect 20 to 40cm of snow to accumulate above 600 metres, with 10 to 20cm possible down to near 400 metres, and lesser amounts to 300 metres.

The snow levels may be a little higher about coastal hills,such as Banks Peninsula and the Port Hills due to the affect of the strong to gale southerly winds coming of the sea.