“It has been a relentlessly warm year across essentially all of California.
Not only is 2015 California’s warmest year on record to date (beating the previous record set all the way back in 2014), but the details of the persistently elevated temperatures have been particularly oppressive. Heatwaves have been a frequent occurrence throughout the state this summer and now continuing into early autumn, but it’s not just afternoon highs that have been stifling: overnight minimum temperatures, buoyed by the incredible warmth of the nearshore Pacific waters, have been far above their typical levels. This has been especially true in Southern California, where water temperatures as high as 80 F (!) have essentially shut off the natural ocean “air conditioner.”
Extremely warm ocean temperatures have also interacted with an unusually high number of atmospheric disturbances to bring highly anomalous warm season precipitation to Southern California. Some of these disturbances have been tropical in nature (most memorably, the remnants of Hurricane Dolores back in July), but more recently the culprit has been a series of erratic and slow-moving cut-off lows. … ”