The National Weather Service extended a flash flood watch for Kauai and Oahu until 6 a.m. Monday.
A weather system west of the state is making the atmosphere "unstable," and could generate heavy showers, forecasters said.
A flash flood watch means conditions are favorable for flash flooding.
Rains pounded the Garden Island Sunday and flooding closed the Hanalei Bridge and several other roads this morning, but the Kuhio Highway has since reopened.
The rains were widespread. About 8.3 inches of rain fell in Anahola in the 24-hour period ending at 5 p.m. today. The Wailua Ditch recorded 7.8 inches; Lihue Airport saw 6.9 inches and 6.8 inches fell in Puu Opae on the west side of the island.
Kauai County crews also reopened Awawa Road in Hapapepe after debris washed on to the road.
State Department of Transportationcrews responded to a report of a roadway collapse on Kuhio Highway near mile marker 22 in Kilauea, a Kauai County spokeswoman said. The right shoulder of the highway heading north is barricaded until repairs can be completed.
The following roads below were closed due to flooding Sunday: Hoone Road, Weli Weli Road, Hapa Road, and Ala Kinoike in Koloa Town.