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Rain arrived over parts of Southern California overnight, bringing a threat of thunderstorms to the region Monday morning.

The monsoonal moisture began moving into the Southland throughout the day Sunday, according to the National Weather Service.

Heavy downpours were falling during the early morning hours over areas of Los Angeles County, as well as the Inland Empire.

A flash flood watch has been issued for parts of Los Angeles, Ventura, San Bernardino and Riverside counties through 8 p.m. Monday.

A flash flood warning is also in place for Riverside County until 9:30 a.m. Monday, according to the Weather Service.

About a half inch of rain is expected for most parts of Los Angeles County with higher totals possible in areas that get heavier downpours and thunderstorms.

Link to Los Angeles County rainfall totals

More than an inch of rain had already fallen in some Riverside County mountain areas Monday morning.

Link to San Bernardino/Riverside/Orange county rainfall totals

There is a slight chance of flash flooding and minor debris flows over recent burn areas, particularly across the Los Angeles and Ventura county mountains, and the Antelope Valley, the Weather Service stated.

Commuters are reminded to use caution when driving as roadways can become slick, especially after long dry periods.

Some lingering showers are expected to continue into Tuesday before drier weather arrives. Mostly sunny skies return to much of the Southland on Wednesday.