Jenn, sorry to be a bit late to answer. I've also read your other post about moving, and am putting my thoughts together fo a useful answer.
Rachy nailed the "seasons" very well. I'll add that in the Valleys (San Fernando, and San Gabriel especially) the air quality is not fab in the summer/fall, especially during fire season.
DH and I have lived in Pasadena for 20 years. He's worked at Disney in Burbank the whole time. Prior to that, a couple of years in SF, and NYC before that! And I "lagged" each move for several months. So hopefully I'll have some useful thoughts for you!
Though I spent my first 12 years in SoCal, I am not a summer person! I don't tolerate the heat and,now, for health reasons, stay out of the sun. I crave sweaters and leather jackets! So summer, especially now that I'm no longer working, is pretty much a make-do season for me. Tees, light chinos, sneakers. Sometimes a light white linen long sleeve shirt layered over a tank. I try to jazz it up with interesting colors, or cuts, my favorite stripes, long gauzy/linen scarves. Though I love to buy, I end up beong a big repeater of a few favorites. I did enjoy my summer office wardrobe - navy, white, ivory, poplins, silk, and a swell lime green leather tote that I happily used for many summers.
But always glad for any hint of cooler temps in Sept/Oct, always a bit grouchy when Halloween was hot and the pumpkins rotted : )
I remember you were checking out Poetry a while a go - their linen things work nicely here.
Any way, I certainly hear you about the summertime blues! Maybe a new scarf or a couple of special tops for the vacation?