Severe weather warnings have been upgraded today as heavy rain begins to fall in the South Island and winds of 150kmh are possible in some areas.
While the South Island looks set to bear the brunt, forecast gales and rain have prompted flood warnings for both islands over the next few days.
Trampers and holidaymakers should expect rising rising rivers and streams following recent torrential downpours along western and alpine areas of the West Coast and inland areas of the South Island, Weatherwatch.co.nz said.
MetService has issued rain and wind warnings with gusts expected to top 150kmh in parts of Canterbury, and 140kmh in Marlborough as well as Wellington and the Wairarapa from today.
Otago can expect gusts up to 120kmh.
Rain, stronger winds and gales would hit central parts of the country and exposed parts of Northland and Auckland before moving to the South Island, MetService spokesman Ramon Oosterkamp said.
Heavy rain is expected in the west, and gale or severe gale northwesters in the east from today.
"The western and alpine areas of the South Island may see another period of heavy rain, which may pose problems to those areas affected by the wet weather of last week," he said.
About 300mm of heavy rain is expected to fall in the same catchment areas of the Southern Alps that were drenched last week.
The deluge has prompted Environment Canterbury to issue flood warnings, while the New Zealand Transport Agency (NZTA) has closed part of State Highway 94/Milford Rd as a precaution against rock fall.
Campers, farmers and other landowners in the area have been told to monitor the situation closely as rivers could still become unsafe from floodwaters flowing rapidly downstream.
NZTA Southland state highway operations manager Peter Robinson said the Milford Rd was closed between the Homer Tunnel and Murrell's Bridge from 7pm today due to the heavy rain forecast in the area.
Heavy rain in Westland, Nelson and Buller last week washed away a bridge and caused holiday traffic mayhem.
The wild weather washed out a section of Wanganui River bridge at Harihari, south of Hokitika, on Wednesday, forcing holidaymakers to make lengthy detours.