The worst of the wet weather should be over by dawn tomorrow, Hokitika weather observer Mark Crompton says.
The heaviest rainfall is expected this evening and especially after midnight.
Mr Crompton said the Metservice was still predicting rainfall of up to 300mm inland.
"That's in addition to what's already fallen. The problem is, if we get this heavy burst tonight, it's going to be falling into catchments that are already totally saturated," Mr Crompton said.
"There's certainly scope for flooding."
Up to 9am today, 17.5mm fell in Hokitika and 38.6mm in Greymouth.
Mr Crompton said the worst of the rain should have passed by dawn.
"By the time people are getting up it should have eased across the
The rain would be followed by cooler, breezy south-westerlies and showers.
The weather has forced the Ross Sale Company and IHC Ross Cattle sale to cancel the annual sale set down for tomorrow morning. It has been rescheduled for February 16.
Meanwhile, the temperature in Greymouth finally passed 20C yesterday - for just the second time this month.
- Greymouth Star