MetService has lifted all weather warnings for the West Coast as heavy rain there has eased.
Thunderstorms and strong winds on Wednesday caused widespread flooding.
Forecaster Andy Downs said while there are still some showers along the coast, they would weaken throughout the day.
He said Friday is likely to be dry, except for the most southern parts of Westland and Fiordland.
Nearly 600mm of rain has fallen on the West Coast during the past two days.
The abutment to a one-lane bridge on State Highway Six, just north of Harihari, was washed away on Wednesday.
NZTA West Coast area manager Mark Pinner told Summer Report the road can be rebuilt, but engineers still have to check if the bridge pylons were undermined.
He said that at best it will open on Friday, but this may take longer if the bridge's foundation have been damaged.
A broken fibre optic cable near the bridge that left people in neighbouring towns unable to make or receive phone calls or access the internet, is now repaired.
Chorus said a temporary fibre cable has been laid across the river and a permanent fix will be made in the next few weeks.
Westland District Civil Defence manager Richard Simpson told Summer Report that supplies cannot be transported from Greymouth to tourist operators in south Westland.
Meanwhile, State Highway Six from O'Sullivans through Inangahua - Westport is closed because of flooding and slips.
State Highway 69 from Inangahua - Reefton is also closed, as well as State Highway 65 from O'Sullivans - Springs Junction.
A slip on State Highway 65 near the Shenandoah Saddle has cut power to 65 houses between there and Springs Junction.
Network Tasman said power should be restored late on Thursday afternoon.