Before parts of Wanganui flooded in October 2013 the river level at Pipiriki reached 14.7m, though Mr Smith said stopbank improvements had been made since then.
Wanganui received 37mm of rain on Wednesday, more than double that on any other day this year.
The situation could change and Mr Smith encouraged people to check the MetService website.
He had also contacted the Waimarie Trust so it could plan for the rise of river levels. All river users should be aware of the potential for debris to be washed down the river, Mr Smith said.
MetService is forecasting more rain today but clearing for the weekend, then rain returning next week.
Meanwhile, two accidents in Wanganui yesterday were attributed to wet roads, Constable Trevor Scarrow said.
"It's like driving on marbles, there's no traction there."
After a dry summer, the oil and rubber left on roads makes them slippery when the first large amount of rain falls.
Mr Scarrow said drivers needed to double their following distance in the wet.
"The two-second rule becomes the four-second rule," he said.
"Don't expect your car to behave like it does in the dry."
