Heavy rain, which has already forced the closure of Fiordland's Milford Track, is expected to make its way up the South Island today, accompanied in places by powerful winds.
Some southern holidaymakers are being warned to keep a close watch on rising river and lake levels. They include hundreds of people camping in the Waitaki Valley, who are facing the possibility of a holiday wash-out. Although a flood alert had not been put in place, ECan's South Canterbury duty flood controller, Tony Henderson, said holidaymakers should be wary.
''We've been told between 150mm and 200mm of rainfall could fall in the catchments of both the Waitaki and Rangitata Rivers between now [Monday] and about midday [today].
''It is vitally important holidaymakers who are camping or simply visiting high country lakes and these two rivers keep a very close watch on water levels.''
The Department of Conservation issued a ''high alert'' for the Young Valley in the Mt Aspiring National Park on Monday in advance of the expected heavy rain.
The level of the valley's lake - created by a landslip in 2007 - had risen by more than a metre on New Year's Eve.
Trampers are being advised not to camp on the valley floor and to move through the valley as quickly as possible. MetService duty forecaster Larissa Marintchenko said the heavy rain which plagued Fiordland and Westland yesterday would spread north to Nelson and the Buller region tomorrow, where about 120mm of rain could fall. A severe weather warning for gales remained in place for inland parts of Otago and Canterbury.
The strongest winds - gusting up to 140kmh - were likely around inland parts of central and north Otago, as well as around inland Canterbury.
Canterbury should also expect rain, she added.
More than 250mm of rain - the heaviest amount in the past 12 months - closed the Milford Track yesterday, walkers spending an extra night in the three huts.
It was hoped the weather would clear enough today so walkers could be taken by helicopter to safe parts of the track.
No new walkers started on the track yesterday.
The rain has also closed the Milford road since 4pm on Monday.
New Zealand Transport Agency regional state highways manager Ian Duncan said conditions would be assessed this morning to determine whether it could be reopened.
''We thank the public for their patience and understanding while the road is closed.''
There was also a warning from Environment Southland for trampers and campers in the Mataura and Oreti River areas. Duty officer Wendy Barrow said flood warnings were issued for the upper reaches of the Mataura.
''Our first concern is for trampers and people camping alongside the Mataura and the Oreti, and their tributaries, particularly in places like Nokomai and Cattle Flat. They need to be aware that the rivers are rising rapidly,'' Ms Barrow said.
As the flood peaks travelled downstream, they would also affect the middle and lower reaches of both rivers, so farmers should consider whether they needed to shift stock, she said.
