Tips for staying warm?

Hi everyone! This is only my second festival ever. I’m planning my outfit and knowing California’s weather, I’m assuming the high is going to be around 60ish and it could drop as low as 40°. I really want to wear a typical rave outfit for women that doesn’t have a lot of coverage but I’m wondering how you guys stay warm?? Will I be able to bring additional layers in my bag? Thanks in advance:,)