CHP and fire personnel respond to a big rig crash along the westbound I-10 freeway in San Bernardino November 29, 2012. The California Highway Patrol issued a Sig Alert at 7:47 a.m. after a semi- truck hauling pallets of candy crashed into the center divider of the freeway between the I-215 and Waterman Avenue. (GABRIEL LUIS ACOSTA/STAFF PHOTOGRAPHER)

It will be a wet weekend and, if Thursday was any indication, a dangerous one.

Rain is expected to continue on and off through Sunday night across much of Southern California. A storm system is expected to move in over the San Gabriel Valley Friday, bringing with it a 40 percent chance of rain, National Weather Service spokesman Stuart Seto said.