Lance Johnson, visiting from Albuquerque, NM., swings his niece Elsa Schulte,3, of Redondo Beach, just south of the Redondo Beach Pier. The beach got an F for the winter months and a C during summer in Heal the Bay's annual report card. (Jay L. Clendenin / Los Angeles Times / May 23, 2013)

May 23, 2013, 8:34 p.m.

Southern California beaches had overall good water quality during the last year, and a vast majority of beaches received good to excellent ratings, according to an annual report released Thursday by Heal the Bay.

The organization's beach report card was first published in 1991 and assesses water quality at more than 600 beach monitoring locations on the West Coast.

Each location is assigned an A to F grade. The higher the grade, the lower the chance of becoming ill while swimming in the water.

Southern California beaches that received A ratings during summer and dry winter periods included Santa Monica Beach at Wilshire Boulevard and Will Rogers Beach at Temescal Canyon, the report by the Santa Monica-based environmental organization found.

Some beaches received A+ ratings. They included Hermosa Beach, Cabrillo Beach in San Pedro and the Wedge in Newport Beach.

Among the beaches receiving F grades were Doheny Beach in Dana Point, Avalon Beach in Catalina and the beaches adjacent to the Redondo Beach and Malibu piers, according to the report.

Grades are typically lower during rainy periods. The report noted that Southern California experienced rainfall totals well below average last winter, resulting in improved water quality.

"Rainstorms greatly increase the amount of urban runoff, the greatest source of bacterial pollution at local beaches," Heal the Bay officials said in a statement.

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Many Southern California beaches get top grades, report says