Around 115 motorists will remain stranded in their cars near Fox Glacier overnight.
Police and West Coast Civil Defence earlier responded to reports of several motorists struck on State Highway 6 between Franz Josef and Fox Glaciers.
The motorists were stuck in the middle of a road closure due to gale-force winds and falling trees.
NZTA closed SH 6 from Ross to Makarora at 10.30am and it was expected to be closed until further notice.
Emergency services had been in radio contact with the stranded motorists and there was no immediate
danger because they had water and shelter.
They will receive assistance as a priority first thing in the morning as conditions allow.
Much of the fury of ex-cyclone Fehi had now passed over New Zealand, leaving a trail of flooded homes, torn-up roads and displaced Kiwis in its wake.
But as some regions begin cleaning up the mess, forecasters are warning areas like the West Coast of the South Island are not off the hook quite yet.
Metservice Meteorologist Sarah Haddon said the main system affecting the South Island today had moved away to the south west.
However, Haddon said a low would stick around, continuing to drive some nasty weather into the already soggy Westland area.
"The West Coast will continue to see some really heavy rain fall and strong winds," she said.
"They're not off the hook yet."
A heavy rain warning remains in place for Westland and the Canterbury High Country well into tomorrow morning.
Several regions hit hard by flooding remain on high alert tonight with another high tide imminent.
South of Auckland, in the coastal community of Kaiaua, residents were being encouraged to prepare for the possibility of flooding.
The small town was hit hard by flooding early last month when a storm that coincided with a king tide waves caused waves to burst over the sea bank, affecting hundreds of homes.
In Westport, a welfare centre set up for evacuees earlier in the day will remain open until 3am.
The nearby town of Granity was also pounded by the storm. Homes were flooded with sea water and some residents headed to Westport to escape the carnage.
Waves washed away a temporary stop bank and water flooded the streets.
Dunedin Civil Defence was keeping an emergency line open for those with concerns about flooding.
With the low expected to settle in tomorrow would come a "significant drop" in temperatures over the country, Haddon said.
The South Island was worst hit by the storm today - with Civil Defence declaring a State of Emergency in both Dunedin and the Buller District.
The Dunedin City Council prepared to evacuate residents this afternoon with around 800 homes at risk of being inundated with sewage-contaminated floodwater.
Police were visiting properties affected by wastewater overflows around South Dunedin to let people know that an evacuation centre was available if needed.
The rain presented a dramatic turn-around for the Otago region, where a huge blaze ripped its way through a chunk of forestry and incinerated several industrial buildings on Wednesday night.
About 100 residents were evacuated when the fire took hold of the suburb of Burnside.
The West Coast was also battered with a deluge of torrential rain and strong gusts today - enough to cut the region off the grid.
Some residents in Hokitika and the surrounding area were expected to be without power for up to 48 hours.
Dozens of campers were forced to flee the grounds of the local Racecourse in Westport this morning after a "mini tsunami" of floodwater inundated the track.
Westport South, North and Buller High School would also be closed tomorrow, following a directive from the Ministry of Education to close as a precaution.
While Christchurch escaped the worst of the weather event, the area was hit with strong winds and rain. Thousands of homes were without power in the Selwyn and Halswell areas, though residents were expected to be back on the grid tonight.
Christchurch firefighters also battled several unrelated fires over the afternoon.
Wellingtonians were forced to battle gale force winds with gusts up to 160km/h and heavy rain this afternoon.
Flights were cancelled, as were ferries and a handful of train services.
A backlog of angsty passengers could also be expected further north tomorrow after a raft of flights scheduled for departure from Auckland airport were also cancelled.
Auckland was expected to get another dumping tonight as the remnants of Tropical Cyclone Fehi continued to hammer the country.
MetService rain radar shows a huge rain cell tracking over the region.
The city could see a repeat of the chaos that hit this morning, when Tamaki Drive was closed after storm surges flooded across the road.