What to wear in Southern CA in September?

Hey! I'm figuring out my wardrobe for a trip to southern CA this September and I need outfit ideas! I haven't been to CA in years and have no clue what the weather will be like. I can't do things like wedges/heels as we'll be doing lots of walking and things like the disney parks, sea world etc. I'm a High schooler, Slim, Petite (around 5') and Asian, with dark hair/eyes and golden undertones. Basically I don't wanna be freezing cold, burning up or look like a frumpy tourist. Tips on quick effortless CA style hair and makeup would be appreciated as well. Thanks!