An active weather front sweeping across the country this weekend is set to bring heavy rain, strong winds and a burst of unseasonable warmth – before a sharp winter chill returns.

MetService has issued orange heavy rain warnings for parts of the South Island, including Fiordland, the Westland Ranges and the headwaters of Otago and Canterbury lakes and rivers, with torrential falls expected from Friday evening.

Forecasters warn intense rainfall in these areas could see rivers rise rapidly, increasing the risk of flooding, slips and hazardous driving conditions.

A strong wind watch is also in place for Southland, inland Otago and western Clutha as powerful northwesterlies build ahead of the system, MetService said in its latest weather update, with more watches and warnings expected to be issued in the coming days.

The weather front is already forming over the Tasman Sea and is due to move north across the country over the weekend, MetService says.

It will first hit the South Island on Friday and Saturday, before spreading across the North Island by Sunday.

For the Bay of Plenty, MetService says conditions will deteriorate later in the weekend.

Fine weather is forecast through Friday and much of Saturday, before northwesterlies develop and cloud increases. Rain is expected on Sunday as the front pushes north.

The system will also drag warmer air over the country, lifting temperatures well above average for this time of year through the weekend, before colder air sweeps back in behind the front, according to MetService.

Strong winds are expected to affect central parts of the country by Saturday, including Wellington and Wairarapa, where gusty northwesterlies could make conditions unpleasant and disrupt travel.

By Sunday, the weather band is forecast to cross the North Island, bringing periods of rain and heavier falls in central areas, particularly around higher terrain.

Despite the soaking forecast for western regions of the South Island, eastern areas are expected to see less rainfall, with strong winds likely to be the dominant feature.

The unsettled weather is expected to clear from the South Island by Monday, replaced by colder, frosty conditions as winter reasserts itself.

However, forecasters say further turbulent weather could return later next week.