Swollen rivers in Canterbury and Otago are being closely monitored following heavy rain this week.
Torrential rain battered the South Island regions on Tuesday, closing schools and kindergartens, crippling traffic and forcing farmers to move stock to higher land.
In North Otago, up to 300 millimetres of rain was expected to fall in the Kakanui/Dasher catchment overnight on Tuesday.
The rising Kakanui River was flowing at 956 cubic metres per second late on Tuesday night and the Kakanui Bridge has been closed since 7pm.
The Waitaki District Council's Civil Defence spokesperson, Rowan Carroll, said Kakanui Hall has been put on stand-by as an assembly point for evacuees.
Many parts of State Highway 1 in the region are closed on Tuesday night, as are State Highways 82 and 83.
Ms Carroll said unless people are advised to evacuate, they should stay where they are and avoid travelling unless absolutely necessary.
Close attention is being paid to rising river levels and early morning high tides in coastal parts of Otago and South Canterbury.
A strong swell of up to four metres high has pounded the coastline. The Canterbury Emergency Management Centre says the easterly swell could create a build-up of shingle at river mouths meaning swollen, fast-flowing rivers have no access to the sea and could flood.
The Otago Regional Council is monitoring rising levels of the Shag and Waikouaiti rivers, while in South Canterbury there are concerns about the stopbanks of the flooded Waihao River.
The MetService said the rain was expected to ease significantly in North Otago and Canterbury on Wednesday.
Meanwhile, heavy rain in Marlborough and Kaikoura was expected to ease on Tuesday night. However, another 40mm to 60mm could fall in the ranges and people are being warned look out for slips, surface flooding and rising rivers.
South Island road closures
Civil Defence in North Otago has advised motorists to avoid driving in all parts of the region. Many roads and highways are closed due to flooding.
Civil Defence said there is no access to Oamaru from the north but there is a detour from the south through Deborah on the coast road.
State Highway 1 is closed south of Oamaru at Maheno and Palmerston, and there is flooding over the road at Big Kuri Creek in Hampden.
There is also surface flooding at Waikouaiti at the Karitane turnoff, leaving possible strandings between Palmerston and Maheno.
Motorists are advised to take care on State Highway 1 between Clarence and Oaro, and on State Highway 6 from Harihari to Haast.
North Island flooding
In the Wellington area, there was flooding on state highways at Tawa, Churton Park and Petone on Tuesday night and police urged drivers to slow down.
There was extensive flooding in Whakatane with 162mm of rain falling overnight on Monday. The Fire Service said it received 25 flood-related calls from 10pm and water was more than half a metre deep in some streets.
A heavy rain warning has been lifted for Bay of Plenty, Gisborne, Tongariro National Park and Hawke's Bay south of Napier.
Snow on Queenstown ski field
The abrupt change to winter has brought snow to Queenstown's ski fields. The Remarkables ski field has a 15 to 20-centimetre base and more snow is forecast in coming days.
