People could have died when a flood went through a hotel, if it wasn't for the actions of two locals who were monitoring the river, Westland Civil Defence says.
The Waiho River broke its banks late last night, sending floodwaters through the Mueller Scenic Hotel and the Top Ten Holiday Camp, north of Franz Josef on the West Coast.
The hotel has been evacuated and a state of emergency declared.
More on today's wild weather around the country
Civil defence controller Allan Wilson said the two local men had been watching the river, concerned that the stop bank might collapse, and warned people when they saw it start to go.
Mr Wilson said, without them, lives could have been lost.
"That's not worth considering. It really isn't. That could have been disastrous," he said.
"You had, you know, 70 people in there. If that had come through when they were still in there... it's just not worth thinking about."
The same two men later warned the holiday camp when water was headed its way, allowing tourists time to collect essential belongings, he said.
RNZ reporter Conan Young, in Franz Josef, told Checkpoint with John Campbell that work was continuing to try to plug the gap in the river's stop banks.
Diggers were trying to re-route the river away from the hotel with the help of large rocks.
They had a massive job ahead of them as the river was running high and fast, and had deposited large amounts of debris and silt around the hotel, he said.
However, the severe weather and torrential downpours had eased and the Waiho was no longer posing a threat to other accommodation providers.
Hotel guests evacuated last night have been allowed back in to collect their belongings, and those spoken to by RNZ News said there was no damage to their things.
Flooding has also hit Nelson and Tasman, and trees have brought down power lines in Auckland as wild weather lashed the country today.