We've seen 50s and even a few 60s in December in years gone by. What makes our current stretch of warmth unusual is the sheer persistence of the mild signal: day after day, week after week, month after month.
Since Sept. 1 more than 80 percent of the days have been warmer than average, according to Mark Seeley. "Further, if you add in the first 10 days of December, the stretch of days from September 1, 2015, to December 10th is the warmest in state history, a remarkable run of warmth," he added.
El Niño's firehose of moisture has been aimed at the Pacific Northwest, not California. Record warmth is reported out east; there should be enough warm air aloft for rain here on Sunday. ECMWF (European) data suggests a second, heavier surge of precipitation on Monday — possibly warm enough for rain. But NOAA's models hint at rain ending as slushy snow Monday. Timing and amounts are very much up in the air but I could see a couple inches of snow by midweek.
Overdue reality check: By late next week there will be NO doubt in your mind that it's December.