A MetService spokesman said a large and complex low pressure system and associated fronts were forecast to bring periods of heavy rain and severe gales to many parts of the country through to late Sunday.
There would be a period of particularly heavy rain between 11am and 11pm tomorrow, and rainfall accumulations may approach warning criteria, he said.
"People are advised to keep up to date with the latest forecasts in case any changes are made or more areas added."
Meanwhile temperatures have been climbing across the South this morning. Just after 11.30am Mosgiel was the hottest place in New Zealand according to the MetService, reaching 25.4degC. Dunedin was on 24.1degC at the same time and forecast to reach 25degC.
MetService meteorologist Tui McInnes said daytime temperatures could reach near 30degC in some places.
"There's a couple of things that make it a little more complicated, especially the Canterbury Plains and North Otago, their daytime temperatures will be reasonably warm.
"They're likely to get quite strong northwesterlies and as they come over the alps they descend to the plains and warm up."
Temperatures are expected to reach 27degC in Ashburton and Timaru, 26degC in Christchurch and 25degC in Oamaru today.
A number of severe weather warnings are also in place around the country.
An orange heavy rain warning is in place for the ranges of Westland south of Otira and a heavy rain watch is in place for Mt Taranaki, the Tasman and Buller ranges and Fiordland north of Doubtful Sound.
An orange strong wind warning is in place for Wairarapa and Wellington as well as the Canterbury High Country.
Strong wind watches are in place for Queenstown Lakes and Central Otago, Fiordland, Taihape, the Hawke's Bay ranges and Marlborough.
With NZ Herald
