The National Weather Service Honolulu Forecast Office has issued a flash flood watch for the islands of Ni'ihau, Kaua'i and O'ahu.

The weather bulletin, which was issued about 3:30 a.m. today, says a strong low-pressure area is expected to form northwest of Kaua'i today and bring heavy rains to Ni'ihau and Kaua'i tonight. Those rains are expected to reach O'ahu by Thursday morning.

The watch will remain in effect from early Thursday morning until late Thursday night.

A flash flood watch means conditions may develop that lead to flash flooding, the Weather Service said.

Residents should monitor forecasts and prepare action in the flood watch is elevated to a flash flood warning, weather officials said.