Roads remain closed and residents will remain without water or sewerage until at least Wednesday after flash flooding in Central Otago today - and more heavy rain is expected tonight.
Video footage captured the ferocity of flash flooding in Roxburgh as trees and debris were swept under a road bridge.
The small Otago town was cut off this morning after silt-laden floodwaters surged through streets, forcing the evacuation of homes and sending large boulders spilling across roads.
Up to 50mm of rain fell in just 30 minutes in a deluge that forced people from their homes - and trapped others - as the heavens opened above the southern fruit bowl.
This morning State Highway 8 between Millers Flat and Alexandra was closed with sections of the road underwater, with significant damage from slips and debris in and around Roxburgh including a major washout at Black Jacks Creek.
Pupils at Roxburgh Area School were told to stay home today and the school confirmed it would be closed again tomorrow because there was no water.
Central Otago police area manager Senior Sergeant Ian Kerrisk said some roads were still closed and were expected to remain closed until at least tomorrow.
SH8 from Millers Flat to Roxburgh and SH8 Roxburgh to Coal Creek was closed with a bypass in place across the dam and along Teviot Rd to Millers Flat.
No structural issues had been reported as a result of the flooding, he said.
Kerrisk said phone lines at Millers Flat were still out and cellphone coverage was intermittent.
MetService has tonight issued a severe thunderstorm warning for Central Otago near Clyde and Alexandra which warned of thunderstorms and torrential rain in the area between 8pm and 9pm today.
Kerrisk said police were working with the council to prepare for it and assured residents there would be an increased police presence in the town over the next few days to help out.
"It has been a very difficult 24 hours for our community, and we would like to thank everyone for their patience, understanding and assistance during this time."
Central Otago Mayor Tim Cadogan told NZ Newswire it was "lucky no one was killed".
"There was a lot more damage that could have been done in terms of human life."
Cadogan said the biggest concern was getting water to the township after the reservoir pipe was damaged.
Portaloos were being brought down to service the 600 people without toilets and a larger tanker was set up at the local fire station to provide drinking water.
The Central Otago District Council said water tankers would be in Roxburgh this morning with drinking water.
Residents in the northern Lake Roxburgh Village were also asked to conserve water.
The council said the town was on the priority list for power utility Delta to make the water treatment site safe from downed wires.
Any attempts to sort out the water situation would have to wait until the lines were safe, the council said.
Road inspections have taken place this morning. A damaged local road had been opened for those in the Roxburgh area with urgent travel needs but a bridge into the town was not suitable for heavy trucks.
"There is a local road detour for people with urgent travel needs in the Roxburgh area, Roxburgh East Rd and Teviot Rd, between the dam and Millers Flat," said Transport Agency transport system manager Graeme Hall.
"This local road also has some damage so people need to drive carefully. The Roxburgh East Rd is suitable for HPMV traffic [heavy freight] but the bridge into Roxburgh is not suitable for HPMV.
"We encourage all non-essential travellers to avoid this area if possible. Other drivers through Central Otago will need to take State Highway 85 between Alexandra and Palmerston, north of Dunedin."
Earlier Central Otago Police area manager Senior Sergeant Ian Kerrisk said it was hoped Teviot Rd between Millers Flat and Roxburgh would be reopened by lunchtime with contractors working to clear rubble.
Kerrisk said there was significant damage to the region's roads and said there would be a large police presence in the area today.
There were two known washouts on SH8 north of Roxburgh and the road was likely to remain closed for some time.
Police asked people to put off all non-essential travel in and out of the town, with motorists warned once the highway reopened it was likely to be down to one lane with a stop-go sign.
"Police have been very impressed by the amazing community spirit shown by the people of Roxburgh in what has been a trying night for many," said Kerrisk.
Communications in the area had been affected with Vodafone and Spark cell networks both out and some landlines down.
Around 15 people evacuated to the local fire station were able to return home or find shelter with friends before midnight. None of the evacuated houses suffered damage after water quickly receded.
MetService said a large swathe of the South Island from the Nelson Ranges down to Central Otago and the Southern Lakes could expect more thunderstorms laced with hail and torrential downpours this afternoon.
A severe thunderstorm threat also loomed for the bottom half of the North Island.