Four of the residents were taken to the local hospital and the rest spent the night at the ambulance station.
"They had a high tide at midnight last night so just after that was when it got pretty hectic.
"The fire service assisted a lot of other property owners but a lot of them there was nothing we could do there was just so much surface water."
He said it was still raining but it had slightly eased and the fire service were expecting a big clean-up again this morning.
MetService issued a heavy rain warning for the region, lasting until Friday morning.
The most rain was expected in the Westland area where 300mm was expected.
The "significant winter storm" would affect much of the South Island and parts of the North Island through to Saturday, MetService said.
Gale-force winds are expected to sweep Wellington and the Wairarapa - with gusts up to 130km/h.
The wind, which has potential to bring down trees and powerlines, should ease by Saturday morning.
Civil defence is urging people to avoid travelling, with many roads flooded with water.
Several sections of State Highway 6 and 7 have surface flooding and motorists should drive with caution, the New Zealand Transport Association said.
Snow on roads further south have also been closed because of snow as winter hits the South Island.
The closed roads include State Highway 94 from Te Anau to Milford, State Highway 85, State Highway 8, State Highway 79 from Geraldine to Fairlie and the Mount Cook Highway.
MetService tweeted that there had been "huge" rainfall numbers in the region with more than 400mm falling in the last 24 hours at the Hokitika Gorge and 200mm in the town.
Twitter user Amy Glass said the flooding was severe for residents.
"My parents in Hokitika are reporting worst flooding since the early 80s. Water nearly in the house," she said.
Hokitika resident Max Dowell QSM said the town's stormwater pumps now often failed to pump water from low-lying areas into the local river until it was too late, well after the town started to flood.
His garage was a "bloody shambles" after 241.8mm of rain in 24 hours, he said.
Mr Dowell, a retired engineer who helped with numerous local flood rescues and clean-up operations over the decades, said local authorities "don't seem to listen to locals" and haven't fixed the system.
"When the river floods it becomes higher than lower parts of the town. So they installed pumps. The pumps were set up so that they had flood valves on them, so that when a lot of water came into the chambers they would automatically start."
The system worked well for years, he said, but recently wasn't working, he told NZME. News Service.
"It appears that the town has to flood first before someone goes down and turns the pumps on."
He had serious concerns for Plymouth Court rest home and its residents, he said, as the home was low-lying and especially flood-prone.
Grey District Mayor Tony Kokshoorn said the rain was starting to ease.
"We're pretty sure that is easing off now and the rivers are containing the water within their banks," he told Radio New Zealand.
"It's been pretty bad but it shouldn't take too long to fix it up."
