Enjoy the sunshine while it last as a "large trough" of cold weather is set to move over the country, bringing with it rain and gales.

The brunt of the bad weather will hit just in time for the weekend, putting an end to the unseasonably warmer temperatures most areas have been experiencing over the last couple of days.

A strong northwest flow is expected to cover New Zealand from today until Friday, Met Service said, but on Saturday a large trough will move over the South Island bringing a colder southerly change.

"Rain is expected about western areas from Wednesday to Saturday, particularly about the West Coast and the Otago and Canterbury headwaters, where significant amounts of rain are likely," MetService said.


"For Fiordland and southern Westland there is a high confidence for warning amounts of heavy rain on Thursday and Friday and the risk spreads further north into northern Westland, Buller and western Nelson on Friday and Saturday."

There is also a "moderate probability" of warning amounts of heavy rain about Mt Taranaki, the Tararua Range and eastern Bay of Plenty on Saturday and Sunday.

The South Island and lower North Island can expect to see wind gusts rising to gale force at times, particularly about Marlborough, Wellington and Wairarapa on Saturday and Sunday.

"Temperatures become significantly colder about eastern and southern parts of the South Island during Saturday, with snow showers possible to low levels."

WeatherWatch has also warned of gusty winds from Thursday, picking up on Friday.

"This will lift temperatures in some eastern areas of both islands to 20C -- not bad for the first day of August," the forecaster said.

By Saturday the winds ease over the South Island but push into the North Island with gales about Wellington and Wairarapa. However, damaging gusts are not expected at this stage, WeatherWatch said.

Rain will move into the West Coast from Thursday, and likely to turn more widespread later on Friday and Saturday, it predicted.


"For the most part Saturday looks fairly dry in the North Island but rain moves in, slowly, on Sunday for western and northern areas mostly," WeatherWatch said.

"This includes Northland, however the angle of this rain band means those hit by flooding last time aren't in the exact same position this time, which is good news."

However, it said the rain was "one to watch" due to its slow movement.

"At this stage we don't expect any problems, or at least any serious ones."