LOS ANGELES—A cold low-pressure system from the Northwest has brought rain and snow to parched Southern California.

The National Weather Service says rainfall Thursday has ranged from light to heavy depending on location, and the snow level is expected as drop to elevations as low as 3,500 feet in the mountains.

Three buses crashed on wet Southern California freeways in separate incidents, leaving dozens injured and one person killed, but it wasn't immediately clear if all were related to the weather.

Caltrans says chains or snow tires are being required on some routes in the San Gabriel and San Bernardino mountains.

The system is not expected to drop enough rain on downtown Los Angeles to avoid setting a mark for the driest calendar year on record.