What to wear to a job interview?

I'm a 19 year old college student home for the summer. I have a job interview this week with a law firm, but since this is my first job, I don't know what to wear. I want something youthful but still tasteful, and I don't want to dress too warmly... It's summer in Florida. It's hot. Any advice would be appreciated! Whenever I search online I find tips that I think were designed for older people. Thanks.