The Los Angeles area will see rain starting Wednesday night through Thursday, while mountain and desert spots may experience thunderstorms through the remainder of the week.
"We're looking in the L.A. basin for the risk for a half inch to an inch of rainfall, higher totals in the nearby mountains and also in the lower deserts as well where there could be 1-2 inches of rainfall," AccuWeather chief meteorologist Jonathan Porter said.
"We're most concerned about the greatest risk for flash flooding across the lower deserts and the mountains... especially in any burn scars over the coming day and a half," Porter added.
The heaviest downpours will target the mountains and deserts, but urban areas can also see flash flooding, and slick roads can make for dangerous travel conditions.
The coasts are also under a close eye as thunderstorms that can form will be capable of producing rough conditions at sea.
"Have your marine radio tuned," said Pono Barnes, a captain ocean lifeguard with the L.A. County Fire Department. "Make sure you know exactly what you're getting yourself into as you go out there, and know your limits."