Severe weather warnings have been issued for parts of the country as heavy rain sets to disrupt weekend plans, MetService says.

Nelson, Taranaki and Fiordland through to the Bay of Plenty could expect heavy rain this weekend as heavy, thundery weather crossed the South Island this weekend and the North Island early next week.

MetService meteorologist Daniel Corbett said northern and western areas of the country would bear the brunt of the rain, so "keep the rain coats handy".

The rain and thunder would reach Auckland by Saturday night but temperatures would not be affected, with 20C forecast for Sunday.

Christchurch and Dunedin would reach similar temperatures.

People would have to continue to plan around the wet weather as another storm headed towards the country after that, Mr Corbett said.

The low was likely to bring more heavy rain and strong winds with a risk of coastal flooding, he said.

"This may be a significant event for northern New Zealand, and it will pay to stay up to date."