Rising floodwaters have forced homeowners and holiday-makers to evacuate in Otago and Canterbury, where rivers have burst their banks and torrential rain has washed out roads.
While the raging Ashburton River had spilled into farmland, on Tuesday night Civil Defence staff were confident the town would be spared when the water peaked at the State Highway 1 bridge.
State Highway 8 through Lindis Pass between Tarras and Omarama would remain closed overnight because of fresh snow, slips and flooding, along with the Aoraki/Mount Cook highway and Haast Pass, Waka Kotahi said.
Spokesperson Graeme Hall said people should delay any travel until Wednesday.
Accommodation in places such as Twizel, Fairlie and Tekapo was filling up with the arrival of travellers stalled by road closures, he said.
Earlier, a dozen homes were evacuated and 50 people had to flee to higher ground when floodwaters swamped Omarama's Top 10 holiday park.
Owner Irwin Beiboer said almost half of the units had water damage.
"We have three units that definitely need new carpet, one unit has basically turned sideways - it's been pushed off its foundations - and the rest we haven't been able to access yet," he said.
"We have a river behind us and it's now like the river is everywhere, we can't see any grass."
Streets turned to rivers in nearby Otematata, flooding half-a-dozen homes.
Civil Defence volunteer Brent Cowles said an elderly couple had to leave when water started running through their kitchen, lounge and bedroom.
"We got them into a nice dry place at the hotel and made sure they were warm. It'll probably be a week before they get back to their house I guess, by the time carpets have dried," he said.
Slips and wash-outs cut access to Aoraki/Mount Cook and Lake Ohau near Twizel.
Resident Norm Mackay said there was a gaping hole on Lake Ohau Road where there was once a bridge, trapping holiday-makers.
"The bridge has been completely cut in half, you could not get across. The distance from one side of the bridge to the other would be 30 to 40 feet gone completely, a raging torrent of water in between," he said.
Mackay's weather station had recorded 240 millimetres of rain in the last three days.
"We have never in 30 years here seen as much rain in such a short period of time," he said.
Lake Ohau Lodge owner Mike Neilson told Checkpoint 130 people were stranded there on Tuesday night.
"The village is mostly people that are staying in holiday homes so they're not too fussed at the moment, I guess when it's time to get back to work, that's when they'll be more concerned," he said.
Latest from Lake Ōhau after bridge washed out in wild weather
Mount Cook village recorded 411 millimetres of rain in the 24 hours to 8am this morning, MetService said.
Fourth-generation sheep and beef farmer John Anderson said Ben Omar station near Omarama resembled a lake.
"We farm the north side of the Ahuriri River and it's burst its banks. We've got quite a lot of flat going down towards the head of Lake Benmore and it's all under water," he said.
He had already moved stock to higher ground, but said he was facing a big clean-up.
"It's just going to be a big mess. There will be debris and build-up all over the fences, they'll be flat. All the creek crossings will be blown out, flood gates, it's going to be quite a lot of work," he said.
The Omarama Volunteer Fire Brigade was called at about 6.15pm to clear blocked tanks in Totara Peak Crescent. Photo: Facebook/Omarama Volunteer Fire Brigade
Further north, Civil Defence in Canterbury was dealing with a number of road closures caused by flooding from the Ashburton River which had burst its banks in places.
Ashburton mayor Neil Brown said the town would not flood when the river peaked at the State Highway 1 bridge.
"The risk of flooding in the Ashburton township is very, very low. The stopbanks that protect the town are very good and they will not be breached," he said.
Ashburton River Photo: RNZ / Tessa Guest
While river flooding had inundated paddocks and closed roads, Brown said Civil Defence staff expected about half the volume of water in the river compared to last May's flood.
"Up-country we've had some breaches of stopbanks and water has come out of the river in some places, but nowhere near the extent it came out and the damage it caused last time," he said.
Motorists were being urged to travel only if essential.
The Rangitata, Orari, Lower Waitaki, Rakaia and Waimakariri Rivers were also being monitored by Environment Canterbury.
In Nelson, the main road through Stoke is closed due to surface flooding from heavy rain.
Motorists are advised to detour along State Highway 6. Buses that travel along Main Rd in Stoke have also been diverted along the state highway.