Rainfall is expected across parts of the country earlier in the week, with weather clearing to fine days from Wednesday through next weekend.

On Tuesday, a large trough should cross the country and develop into a deep low south of the Chatham Islands, a MetService forecaster said.

While this is happening, a strong west to southwest flow is expected to spread over mainland New Zealand, bringing a cold change to the South Island with snow to the mountains.

"There is low confidence that during the first half of the day, significant rainfall will affect the Tararua Range, and the districts of Buller, Grey and northern Westland," a MetService spokesperson said.

"About coastal areas of Otago, and mid and north Canterbury, there is low confidence that southwest winds could reach severe gale force."

MetService said there is also mostly low confidence that west to northwest gales could become severe in the east of central New Zealand, from Gisborne to Marlborough including Wellington and the Horowhenua and Kapiti coasts, and also in areas of the Tasman District.

"However for parts of Wairarapa, the Tararua District and Hawke's Bay, the confidence for severe westerly gales increases to moderate.

"Finally, there is moderate confidence west to northwest winds could become severe over the Chatham Islands during the second half of the day."

On Wednesday, April 9, a ridge of high pressure is forecast to spread onto New Zealand with minimal risk of severe weather.

This high is expected to lie over New Zealand on Thursday.

The ridge of high pressure will lie across central New Zealand on Friday, while a front will approach the south of the South Island from the south.

"A trough to the north of the country will bring increasing showers [on Friday] with strengthening easterly winds to the north of the North Island. There is minimal risk of severe weather.