Flood-hit Waitaki residents are now being warned to stock up on food and essential supplies ahead of "blizzard conditions."
Waitaki Civil Defence says exposed parts of the district struggling to clean up from flooding are in the path of a looming cold snap on Thursday and Friday.
"People should stock up with food and other essential supplies before the snow arrives.
"For farmers, animals need to be sheltered from potential blizzard conditions and need to be moved in the next 24 hours to paddocks which are away from floodwaters, landslides and power lines."
Meanwhile detours are in place as the key route to the north of Oamaru remains impassable by floodwaters which had cut North Otago roads and bridges and forced Civil Defence to set up emergency shelters.
State Highway 1 remains closed from Pukeuri to Seven Mile Rd although last night the main highway at Maheno, which had been closed during the day, reopened, first to trucks and 4WDs only and then, from about 8pm, to all traffic.
Much of the Taieri Plains are also under water after persistent rain throughout yesterday, raising fears of what today will bring, although the Taieri River, at Outram, is now dropping.
The Taieri was still rising upstream at Sutton, near Middlemarch, but has now peaked.
The lower Clutha River has hit its first flood warning level at Balclutha and minor surface flooding is expected in low-lying areas.
State Highway 90, from Tapanui to Waikoikoi, was a late addition to the list of main roads closed last night.
In Dunedin more than 25 roads remain closed because of flooding and slips and cautions are in place for state highways north and south of the city.
In North Otago there was concern residents near the Otiake River in the Waitaki Valley could be isolated by rising floodwaters.
Yesterday, between 100 and 130 people went to a Civil Defence shelter at Maheno and a helicopter was used to drop food and blankets to those stranded by the flooding. Other shelters were established in Kurow, Duntroon and Kakanui.
Last night Civil Defence urged residents to stay off the roads unless travel was essential. School bus services today were cancelled and officials warned residents to prepare for more flooding today, as water from heavy rain inland flowed to the coast. A further 20mm of rain was forecast to fall to midnight last night but rain was expected to ease today.
North and East Otago yesterday bore the brunt of the storm with about 70 roads closed.
Several bridges were damaged, including one at Otekaieke in the Waitaki Valley, while a bridge on Danseys Pass Rd, about 14km from the Livingstone turnoff, was destroyed by floodwaters, and the Kakanui Bridge on Waianakarua Rd was closed for safety reasons.
Sergeant Wayne Brew, of Oamaru, said a tree carried by floodwaters crashed into the bridge and a branch broke through the safety barrier.
It would remain closed until engineers had carried out a safety assessment and confirmed the bridge's integrity.
Waitaki emergency services manager Chris Raine said less rain had fallen than during the last major flood in May 2010, but the effect was worse this time.
''In 2010 we were coming out of a dry event, but this time the soil was saturated so there has been more run-off,'' he said.
Waitaki Civil Defence public information manager Elton Crane said 10 crews were sent to assess the scale of the floods across the district, but he warned that because the heaviest rain fell inland, worse was still to come. The situation was expected to become ''fairly serious''.
''Civil Defence has established temporary emergency welfare centres in Kurow, Duntroon and Kakanui for people who are isolated and need assistance,'' he said. The situation was being monitored in Herbert, Palmerston and Hampden.
''There is no safe way in or out of Oamaru and residents are advised to stay in their homes.''
Federated Farmers North Otago president Richard Strowger said some stock had been stranded by floodwaters, but there had been no reports of losses.
''I was talking to one cocky who said all you have to do is catch the baleage as it floats past, so I take it from that there must be quite a bit of baleage going west as well.''
At least three schools in the Waitaki district were closed yesterday.
Maheno School, Five Forks School and the Waitaki Valley School at Kurow were all closed, as 35 school bus routes were cancelled for the day. The same routes will most likely be closed again today.
Conserve water notices were put in place in Herbert-Waianakarua, Hampden-Moeraki, Windsor and Kauru Hill rural water schemes, as well as the Waihemo-Palmerston, Goodwood and Dunback supply zones and the Lower Waitaki, Tokarahi and Stoneburn rural water schemes.
Awamoko rural water scheme consumers were told to conserve and boil water.
South and West Otago also experienced some disruption, with flooding closing several roads around Milton, the Catlins and Tapanui, and farmers forced to shift stock from low-lying paddocks.
The New Zealand Transport Agency (NZTA) advised motorists to be cautious due to water on State Highway 1 south of Milton to the Clarksville Junction.
The Southern Scenic Highway through the Catlins had also been closed at Caber-feidh near Papatowai. Maniototo roads and bridges bore the brunt of flooding in the Central Otago district, with several roads and bridges closed yesterday because of washouts.
A washout caused by the Kyeburn River closed Danseys Pass, so it was impassable at both ends.
''That's always caused challenges for us, as the river flows very swift and shifts its alignment,'' Central Otago District Council roading manager Julie Muir said.
Contact hydro generation manager Graham Quinn said the Roxburgh Dam was spilling yesterday, mostly because of the high level of the Manuherikia River. It was unusual for the dam to be spilling water in winter rather than spring.
Rainfall in 24 hours to 5pm yesterday:
• Dunedin City 72mm
• Dunedin airport 17mm
• Pine Hill 117mm
• Sullivan's Dam 134mm
• Oamaru 51.4mm
• Oamaru Airport 45mm
• The Dasher 183mm
• Kakanui 61.5mm
• Alexandra 20mm
• Balclutha 10.4mm
