Key places to visit in south florida?

i'll be staying with my grandma in fort lauderdale from the 21st of august to late sept. first how is the weather? i really want it to be sunny as i live in seattle, washington and its FREAKING cloudy here EVERYSINGLE day. its 66 degrees over here. so i dont mind heat at all. i'm 19 and traveling alone, so im afraid ill be bored? what is there too do where can i go?