Okay, so when you go to a concert. The most important thing is to be comfortable, and even if you checked the weather for that day you might never know if it's going to be too hot/cold. So if you live where or it's usually burning hot outside, try not to wear black or any dark colors. Black attracts the sun more and you will sweat and burn more likely than if you wear light colors.
And believe it or not if you wear a long sleeve shirt made from a silky fabric you would be cooler than if you wear short sleeves. I wouldn't recommend wearing flip flops either, you'll be in a crowd and people don't care if they stop on you or not. If you expect it to be a little chilly, bring a light jacket with you, something that won't slow you down.
Below are categories for different outfits and tips and such.
What to wear to a concert for:
GIRLS (For Hotter Weathers)
GIRLS (For Hotter Weathers, but for girls who don't want to show as much skin)
GIRLS (For Really Cold Weathers)