Below is the detailed weather forecast as provided by the National Weather Service for Southern California December 2019
Los Angeles
Friday – Sunny, with a high near 63. North wind around 5 mph becoming west southwest in the afternoon.
Friday Night – Mostly clear, with a low around 43. West northwest wind around 5 mph becoming calm.
Saturday Sunny, with a high near 62.
Saturday Night – Mostly clear, with a low around 43.
Sunday – Sunny, with a high near 61.
Riverside
Friday – Sunny, with a high near 58. North wind 15 to 20 mph, with gusts as high as 30 mph.
Friday Night – Mostly clear, with a low around 39. Calm wind becoming east around 5 mph after midnight.
Saturday – Sunny, with a high near 59.
Ventura
Friday – Sunny, with a high near 62. Calm wind becoming north northeast around 5 mph in the morning.
Friday Night – Mostly clear, with a low around 42. Northwest wind around 5 mph becoming north northeast in the evening.
Saturday – Sunny, with a high near 60.
San Diego
Friday – Sunny, with a high near 59. Calm wind becoming west around 5 mph in the afternoon.
Friday Night – Mostly clear, with a low around 46. Calm wind becoming east around 5 mph.
Saturday – Sunny, with a high near 61.