Saturday's high is expected to be around 95-degrees. Storms are possible Saturday evening and overnight after cold-front moves in, bringing temperatures down into the 80s the rest of the weekend.
Organizers of the show have misting stations set up around the festival to help concert goers keep cool.
In effect this year, higher security fences were put in to protect the Grant Park grounds and build a barrier. On Friday, a group of gate crashers tried to hop a fence at Monroe and Columbus and police said tickets were given to some violators.
Police made at least 13 arrests on Friday for various misdeameanors. They also issued nearly 40 tickets for ordinance violations.
With 300,000 people expected over the three-day event, Lollapalooza is seeing its largest crowds ever.
Tonight Jane's Addiction will take the stage. That's the band of Lollapalooza founder, Perry Farrell.
Lollapalooza, which is in its 21st year, has been at Grant Park for the last eight years. New for the 2012 Lollapalooza: live streaming on youtube.com/lollapalooza and Instagram photos from festival goers on jumbo screens within the park.