Oahu, Kauai and Niihau are under a flash flood watch until 6 p.m. Sunday, the National Weather Service said Saturday.

"Heavy showers and thunderstorms continue to affect Niihau and Kauai and may spread to Oahu later tonight or Sunday as a slow-moving front from the west advances toward Kauai," forecasters said this evening. "The potential of flash flooding will remain high as the moist and unstable air

mass associated with the front persists."

The weather service also issued a severe thunderstorm watch for the waters surrounding Kauai until midnight.

Forecasters say the weather system that’s bringing rain to Oahu and Kauai should weaken Sunday night and trade winds should return by Tuesday.

The weather service encourages people to stay away from areas prone to flooding such as streams, drainage ditches, and low-lying areas. Drivers should be cautious on the roads and not cross fast-flowing or rising water.