The blaze at Waikari Valley was still uncontrolled on Monday morning and has now jumped the containment line.
Strong winds on Monday afternoon have also ramped up the vegetation fire.
Households have been evacuated from Shell Rock Road and Glenmark Drive.
Civil Defence said about 10 people spent the night in the welfare centre at Waipara Memorial Hall, while others slept in caravans outside.
Most residents are unable to return home. Some Sealeys Direct Rd residents were set to leave their homes but were able to stay after the fire changed direction.
Earlier, firefighters said the blaze had largely burnt out but remained at risk due to high winds.
But Hurunui Mayor Marie Black told Midday Report a recent briefing by Fire and Emergency New Zealand (Fenz) for evacuees revealed strong north-west winds had seen the fire "billow up a bit".
Black said crews were continuing with helicopters and fixed-wing aircraft to manage the blaze as best they could.
Because of the flare-up, evacuation orders will remain in place for the time being.
Black said recent dry weather had "exacerbated" the fire risk across the region and many residents were living on a knife edge because of the risk and danger it posed.
She was not aware of any resourcing issues given the two large blazes - but acknowledged the work of volunteer firefighters who were carrying a heavy burden to protect their community.
It's the second large fire to break out within a week in the region; crews are still working to extinguish a massive blaze on the Port Hills that broke out on Wednesday.
Fenz is working with displaced residents and farmers and hopes to get them home as soon as possible.
Firefighters continue work to contain blaze
Ground crews were strengthening the containment line of the Waikari Valley fire while helicopters worked from the air.
There have been no reported livestock losses, or any structures lost or damaged.
Fenz said it was working with the residents, as well as farmers in the area, to allow them back as soon as possible.
Glenmark Drive residents Mandy Burrows (left) and Elaine McCarthy with Isla were evacuated to the Waipara Community Hall at the height of the fire in the Waikari Valley. Hurunui Mayor Marie Black and Alf Smith, also of Glenmark Drive, were also at the hall. Photo: Supplied by the Hurunui District Council
Evacuees saw flames coming down the hill
Evacuee Louise Smith was worried about her landlord's farm but heard the stock had been moved to safety.
"At 3 o'clock this morning, my partner could see the flames coming down the hill and it was just really windy which was quite worrying for the firefighters and stuff and everyone helping."
Les Winslade said he was waiting to get home to check on his livestock. He has eight cows on a lifestyle block that he hopes have survived.
"It's a bit of a worry because way back in 1989, me and the wife had an experience where our house burnt down and we lost animals in the fire so it's a bit traumatic for us.
"It brought back scary memories."
Winslade said he was grateful for the work of the firefighters to get the blaze under control.
When she went outside, she said the north-west wind was blowing smoke straight towards them.
"Then as time went on, we got a phone call from one of the local fireman and he said: 'Oh, perhaps be prepared that you probably will be evacuated', and then just before midnight, we got a knock on the door from a policeman. We had readied a couple of bags and some precious photos and things and got them in four different vehicles with the farm dog.
"We managed to get the farm dog, but the cats didn't want to have a bar of it so they're still at home.
"I'm pretty sure they would run if it got as far as that. But it did come over the hill, over Mount Donald and hopefully they can contain it today, but the wind's not going to help especially if it's too windy for the helicopters to go up so that's not going to help at all either."
Thompson and her husband stayed in their car outside the Waipara Memorial Hall overnight where a community meeting for residents was held on Monday morning.
Canterbury high country was currently under an orange strong wind warning - with the zone just brushing the Waikari area.
Metservice meteorologist Mmathapelo Makgabutlane said winds could reach up to 120 km/h in exposed area.
Makgabutlane said people in those areas should keep a close eyes on wind speeds.
In a statement early this morning, Incident Controller Dave Key said crews had been working hard overnight to bring the blaze under control.
"From first light crews will be able to assess the fire ground from the air and gain a better understanding of its size."
The helicopters were in the air before 7am.
Flames were "moving through gorse and scrub" in the valley, Key said.
RNZ's reporter at the scene said the fire was in a remote valley and she could see a large portion of scorched grass on one side.
She said there was smoke rolling through parts of the valley with a strong smell of smoke.
Residents from Glenmark Drive and Shell Rock Rd were evacuated.
Those on Sealeys Direct Rd were also going to be evacuated but Fenz said the fire changed direction so they did not need to leave.
HUHANZ (Helping You Help Animals) offered a stock trailer and portable yards to those affected, but said MPI advice advice on evacuating livestock and animals here should be the first port of call. Residents were also posting offers of help on local Facebook pages, including loans of horse floats and paddock space, and crates for pets.
Most of the South Island is currently under fire restrictions, and the dry conditions meant some areas within the Hurunui District Council zone were already under level 4 water restrictions.
In January, Fenz warned the region was tinder dry, the fire risk was the worst it had been in years, and an incident control team was set up in South Canterbury as a pre-emptive measure.
But a cluster of wildfires have already caused destruction this year, including houses and a church destroyed in Loburn, and a number of homes threatened by a long series of fires along a railway line between Aylesbury and Darfield, west of Christchurch.
Port Hills fire update
Firefighting efforts on Christchurch’s Port Hills are continuing into day six, with a focus on eliminating hotspots and strengthening the containment lines.
“Fire and Emergency’s specialist drone team carried out a second night of thermal imaging and identified a further 30 hotspots that crews are targeting today,” Incident Controller Steve Kennedy said.
He said the intention was to strengthen any vulnerable points around the perimeter and continue extinguishing deep-seated fires in several old forestry skid sites before the wind strengthened this afternoon.
- additional reporting NZ Herald and RNZ
