OSHKOSH, WI (WTAQ) - The heat and humidity has now become a greater concern for Rock USA organizers.
Depending on the headliner, between 20,000 and 40,000 come to the annual event that kicks-off Wednesday.
Attendees are being told to stay hydrated.
They can bring in a sealed bottle of water that can be refilled at various water stations.
With conditions right for heat exhaustion, cooling stations and a misting station has been set-up.
Rock USA runs Wednesday through Saturday at Ford Festival Park in Oshkosh.