Keep the rain gear close by.

The wet stuff — with potential for lots of it — could keep O'ahu soggy into tomorrow, according to the National Weather Service.

Heavy clouds had begun to build up along the Ko'olau Range ridge line late yesterday morning, and heavy showers were falling above Pacific Palisades and were expected to drift into the Mililani and Gentry Waipi'o areas, said forecaster Henry Lau.

"The ground there is already saturated and won't absorb any more rain, so runoff becomes a concern," Lau said.

A flash-flood warning was issued for Kaua'i at 6:45 p.m. and was scheduled to be in effect until at least 9:45 p.m. As of 9:10 last night Kaua'i police reported no weather-related incidents.

A flash-flood watch was in effect for O'ahu until 4 a.m. today.

A low-pressure area west of the state is responsible for the wet weather.

Heavy rains late Saturday night and early Sunday morning caused ponding along Kamehameha Highway in Windward O'ahu, especially in the Waikane area.

"The showers actually slackened off overnight, but are building up again now with medium to heavy rain falling now above Pacific Palisades," Lau said.

The Honolulu Fire Department responded to two rain-related calls Sunday and yesterday, spokesman Capt. Kenison Tejada said.

About 8:30 p.m. Sunday, a homeowner on Aialii Place in 'Ahuimanu reported his yard and lanai had flooded with rain water. A section of Kamehameha Highway near Waikane was flooded Sunday night, prompting police to set up a single lane.

Rainfall totals for the 24-hour period ending at 5 p.m. yesterday stood at: