Mt Roy looking over Lake Wanaka on Tuesday morning.

Mt Roy looking over Lake Wanaka on Tuesday morning.
Winter has arrived slightly early in the South Island, with freezing temperatures and dustings of snow in many places this morning.

A midnight storm dumped about a centimetre of snow onto the Porters Alpine Resort near Castle Hill near Arthur's Pass early this morning.

And parts of inland Canterbury and Otago woke to below-zero temperatures, down to -3.2 deg C.

Porters operations manager Blair James hoped the cold snap was an early indicator of good snowfall this season.

He said the dump marked two weeks in a row of snowfall and cold temperatures - weather which makes him hopeful for a good season to come.

Christchurch dropped to 3 deg C early on Tuesday morning and was set to reach a modest high of 12 deg C.

The lowest temperature in Otago at 7.30am today was at Oturehua at -3.2 deg C.

Wanaka and Omarama dropped to -0.6 deg C, while Naseby and Glenorchy hit -0.5 deg C.

"A frosty start to the day for most South Islanders," said MetService this morning.

"Currently, Alexandra is -0.1 deg C, Aoraki Mt Cook -0.9 deg C and Pukaki -3.4 deg C."

MetService said maximum temperatures today will be "cooler than average for this time of year" for many spots across the South Island.

The agency said Dunedin, Queenstown and Wanaka will all only touch the 10 deg C mark.

"So be sure to keep your coat and scarf on hand," a forecaster tweeted.