Flooding, slips possible in South Island amid heavy rain warnings

Flooding and slips are possible with much of the lower South Island under weather warnings and watches as the weekend looms.

MetService has issued an orange heavy rain warning for the ranges of Westland, the headwaters of the Canterbury lakes and rivers south of the Hurunui River, the headwaters of the Otago lakes and rivers as well as Fiordland.

All warnings comes into effect from Friday evening and are in place well into Saturday.

Meanwhile, a strong wind watch is in place for Southland, inland Otago and western Clutha from 9pm Friday until 11am Saturday.

"Northwest winds may approach severe gale in exposed places," MetService said, and there was a moderate change the watch would become a warning.

In a statement, MetService said more warnings and watches over the weekend were possible.

MetService said on Friday, northwesterly winds would begin over the South Island before the rain came.

"Powerful winds are on the cards for some eastern regions for much of the weekend, strengthening about Wellington and the Wairarapa by Saturday.

"Heavy rain is expected for western areas of the South Island on Saturday, and along the spine of the Southern Alps, with thunderstorms possible.

"Heavy rain could spill into the headwaters of the Canterbury and Otago lakes and rivers, causing them to rise rapidly."

MetService said people heading to the Super Rugby final on Saturday in Wellington should wear a rain jacket rather than take an umbrella as showers are expected to turn to rain in the evening - with strong northwesterlies accompanying it.

"By the Winter Solstice on Sunday, this band of rain pushes over the North Island," MetService said.

"Heavier falls are forecast about the Tararua ranges and central parts of the North Island."

Warm temperatures can be expected over the weekend with Christchurch expected to reach 21C on Saturday, MetService said, but it won't last - with a risk of "turbulent weather" on the way.

"Frosty winter conditions return to the South Island on Monday, with a brief period of settled weather."