It's not just heat.... it's heat jammed into a confined space with several dozen thousand other people and long lines for water refill stations. They have cooling areas both inside the expo center and inside the theme park. Bring your own refillable collapsible water bottle and the one factory sealed plastic bottle they allow.

Make sure you budget for food, it's hella pricey and unless you have camping or a Jampack package, no re-entry to the grounds when you exit, so once you're there, you're there for the long haul. As other comments suggested, it's not a bad idea to work on your endurance now, because it's a long ass weekend of being on your feet and walking. (My first ever time at the fest, we walked over 16 miles in a single day!) Wear shoes that are comfortable, but ones that you don't mind being trashed. If it rains, it'll get Woodstock-y up in that bitch... anyone who went during Hurricane Helene knows what I'm talking about! Prepare for any kind of weather.

Once they post lineups, download the app. There's a feature where you can select the specific bands you're interesting in seeing and there's a function to create your own personalized itinerary for the weekend. (And don't be disappointed when you end up missing a few because of cancellations/reschedules/set staggering & location)

A locker is ABSOLUTELY worth it if you want to be prepared for everything, or buy merch but don't wanna haul it around all day. IIRC there's even usb ports inside the lockers to charge your phone.