West Coast Civil Defence says at least 100 properties were without power on Monday morning after heavy rain cut the supply to Fox Glacier and south to Paringa because of a fault on the line from Franz Josef.
However, Westpower said a break in the weather has allowed staff to get into the Fox Hills, where they have found the fault, and power was expected to be restored by mid-afternoon on Monday.
MetService meteorologist Melissa Oosterwijk said further heavy rain was forecast to fall on the West Coast until Tuesday night.
"Considering the amount of rain we've had so far it will just continue, we've also got a moderate risk for thunderstorms for Fiordland and South Westland ... which helps the rain to continue to be heavy."
Westpower said last night due to the bad weather it couldn't get workers to the fault and it would be working on an alternative supply.
Civil Defence public information manager Erica Andrews said the lack of power would be challenging for people in Fox Glacier, where a boil-water notice had been in force since late last week.
"It's very difficult for some of those customers to be able to boil water, but a lot consumers and residents will have gas supplies."
She told RNZ's Morning Report she wasn't aware how many were impacted by the outage but it was "probably a couple of hundred" of households and businesses.
A slip near Thirsty Creek at State Highway 6 has also caused the road to be shut from Haast to Fox Glacier.
Andrews said they were not sure when the road would reopen but expected an update from NZTA this morning.
The only road to Milford Sound has been closed and will not reopen until Tuesday afternoon at the earliest.
State Highway 94 between Te Anau and Milford Sound, has been closed between Cascade Creek and the Chasm due to flooding.
More heavy rain is predicted in the area today and tomorrow.
NZTA said an update on the road reopening would be made at 1pm on Tuesday.
The weather blast comes after the West Coast was hit by a storm in December that damaged roads and cut off settlements on State Highway 6 from Hokitika to Makarora.
