This isn't the first time harsh weather has plagued the annual run. Last year's event saw nearly 2.5 inches of rainfall, according to the National Weather Service, but not nearly as much was expected this time around. In 2011, more than 300 marathon runners were evaluated for hyperthermia and 20 were hospitalized.
Race officials say they're well prepped. Some 23,000 Mylar blankets to help runners guard against hypothermia will be divided among 10 medical stations along the course and at the finish line. Heated buses will also be standing by at the medical stations as well as the finish line.
Despite the chill in the air, more than 20,000 runners battled whatever Mother Nature threw their way and plugged right along. Simon Njoroge of Kenya won the men's division in 2 hours, 12 minutes, 12 seconds. Fatumo Sado of Ethiopia won the women's division in 2:25:39, the fourth-best finish in race history and besting her personal record by more than 2 minutes.
Downtown Los Angeles was at 45 degrees in the early morning hours, making for a chilly start to the day. Things were expected to warm up slightly to the lower 50s through the day with scattered showers across the 26-mile, 385-yard course starting at Dodger Stadium and ending near the Santa Monica Pier.
The "Stadium to the Sea" course takes runners through downtown Los Angeles, hitting Chinatown, Olvera Street, City Hall, Little Tokyo, the Walt Disney Concert Hall and the Cathedral of Our Lady of the Angels.
The course then heads west through Echo Park and Silver Lake into Hollywood, passing the Hollywood & Highland Center, home of the Academy Awards, and Grauman's Chinese Theatre. Runners will then head south onto Sunset Boulevard, entering West Hollywood, and then Beverly Hills, including running on the famed shopping street Rodeo Drive. The latter portion of the race includes Century City, the Veterans Administration grounds and Brentwood's San Vicente Boulevard, and then finally concluding near the Santa Monica Pier.
Street closures for the race began at 4 a.m. Most streets along the marathon route were scheduled to be reopened by noon.
Race officials say rain played a part in three other marathons in addition to last year. There were trace amounts of rain twice in the 1990s and 1.6 inches fell on the race in 2000. The marathon has been held annually since 1986.
City News Service contributed to this report.