MetService has issued a heavy rain warning for a large part of the North Island as warm humid air converges with cool southerly conditions.
The warning covers Taranaki, the Bay of Plenty, the Tararuas and the coastal hills of Wairarapa.
Forecaster Mark Pascoe says a trough crossing the north of the North Island on Friday night is likely to bring a burst of heavy rain to Northland, Auckland, Coromandel Peninsula, Waikato and Waitomo.
He says the heavy rain in the North Island will continue into Saturday - New Year's Eve - but ease later in the day with the exception of Bay of Plenty, where it is expected to persist into the first day of 2012.
Meanwhile, the heavy rain has eased in the Nelson Tasman district.
The rain isolated about 40 people in Golden Bay when the Wainui river burst through a sea wall and inundated a dairy farm and the Tui community.
Nelson Tasman Civil Defence co-ordinator Jim Frater says it is not clear how long it will take to make the land passable, but he estimates it will cost thousands of dollars to redirect the 900 metre stretch of the Wainui River.
Susan King, who runs the dairy farm, says her land was flooded during the record rain falls two weeks ago and now work will have to begin again to fix the latest damage.
She says it will take some time to put things right but it is fortunate that no one lost their life and she feels lucky there has been no damage to her house and the water supply is unaffected.
In the meantime, Ms King says, she is relying on aid from Civil Defence.
The latest rains, coming on top of previous record downfalls, have also caused further land slips on the Wainui Hill and Iwa Road.
Road closures in Nelson city
Rocks Road is closed by a slip between Richardson Street and Bisley Avenue and will not re-open until the slip is cleared and a geotechnical assessment made.
Authorities braced for the worst when rain was forecast, as many areas were still waterlogged from the major storm two weeks ago.
However, Nelson mayor Aldo Micchio says the Tasman Nelson region escaped relatively unscathed.
Only minor slips have been detected, he says, and the major slips from the storm two weeks ago have held up over the past 48 hours.
He says work will now start on ensuring those slips remain stable.
The weather has also had an impact elsewhere.
Rain in Auckland restricted section play in the men's singles and women's pairs of the National Lawn Bowls Championships.
The cancellation of games forced organisers to qualify all the men's singles players for post-section play, while women's pairs teams with 2 or more wins will also be considered to have qualified.
Those matches will start on Monday.
There was some surface flooding in Wellington, where the council asked people to help by clearing drains.