A stormy system will this week develop near the South Island and bring all sorts of weather to the country, says a WeatherWatch spokesperson.

Everything from warm nor'westers to wintry southerlies, sunshine, showers, rain and snow is expected.

"Monday kicks off with a cold front clearing the nation to our east, with a windy west to south-west change behind it," says a WeatherWatch spokesperson.

"Tuesday is cooler but drier for many."

Colder air is forecast to move up the South Island on Tuesday, bringing a few showers to the country.

Wednesday has light winds over the North Island and morning fog patches inland, but windy nor'westers kicking into the lower South Island with possible gales. Most places are dry.

"Thursday sees a cold front crossing NZ, possibly not until night time in parts of the North Island, bringing widespread rain and showers for a time.

"Rain is expected in many dry regions - but not all. Snow levels lower in the South Island but looks to remain above most main centres."

On Friday, rain is expected to ease in the north, slowly clearing over the North Island during the day.

"But it will remain unsettled and wet in many other places as the low near West Coast deepens further continuing rain and snow in the south.

"At this early stage serious snow looks to be above most main centres but it's marginal."

WeatherWatch says the placement of the low pressure zone is key.

"For it to bring serious snow to sea level across the South Island the low pressure zone should be east to south-east of the South Island... at this stage it's forecast to be north-west of the South Island and that tilts the coldest air into the Tasman Sea area."