It's the whole el nino thing messing with the weather. I'm really wanting some 70 degree days!
Bring clothes you can layer. Bring at least one pair of shorts, bring some long pants, bring both long and short sleeve shirts that you can wear together if it gets cold, bring a jacket (one with a zip out liner works great, and if it's waterproof, even better), and don't forget the swimsuit. Then you have all the bases covered. As crazy as the weather has been, those people who make the pants with the zip off legs that make shorts should be raking in the money.