Mentioning the weather, although we are in summer, one of the mostly encountered cases is rain. I know many people's fun times were ruined, because they didn't take the necessary precautions. So, I recommend you to bring your raincoat and rain boots and an umbrella. And there is the sun fact during the day. You must bring a sunscreen with high SPF. You don't want to have sunburn, do you?
Of course a high-quality camera is a must. So, you can take pictures and record videos of your favorite bands and tell your friends "Yes, I was there!" :).
Above all, bringing liters of cold water in a flask is very vital. There will certainly be stands who sell food and beverage, but as far as I know, in such places everything is more expensive. Thus, keeping the water at a reachable place is more advantageous ;)
If you love festivals and want to buy all the essentials, see the selection. HAPPY FESTIVALS!
* This post is in association with "Very".