The concert featured Lyfe Jennings, Chris Brown, Keyshia Cole, Kelis, Jagged Edge, Robin Thicke and others. It reportedly drew 12,000, but took place in 112 degree weather. The overheated spectators prompted the Concord Police Department to activate its mass casualty protocol, a police spokesman told the Contra Costa Times.

The fire department set up a triage center for the 153 heat victims, and 35 were reportedly sent to the hospital. The stage ran on generator power, and the concession stands ran out of ice, according to the Times. Bottled water was reduced from $4 to $1.

The venue staff set up misting tents and temporary showers, but the show ran from noon to 4:30 p.m. and the direct sun wore down many of the concertgoers. A call for backup reportedly brought ambulances to the scene.

“People were fainting all over – even in the parking lot,” a concertgoer told the Times.

Two nights later, Sleep Train held a Crosby, Stills, Nash & Young concert without incident. California’s heatwave was still in full force, but CSNY had a 7:30 p.m. starting time.

KMEL has another daytime concert scheduled at Sleep Train August 6.

Calls to Live Nation’s Rick Mueller and venue spokesman Aaron Siuda were not returned at press time.

In Central California, where heat reached record highs, Michael Bublé played to a Fresno crowd July 22 in a room that was estimated to be 100 degrees.

The air-conditioning unit that cools the 2,300-capacity William Saroyan Theatre as well as nearby Selland Arena failed prior to the event. Outdoor temperature was estimated at 112 degrees. Patrons were given bottled water, but many concertgoers left before the show finished.

To his credit, Bublé did not refuse to perform in such conditions and, although he told his band members that they could remove their jackets, he kept his on throughout the performance.

Saroyan GM William Overfelt apologized to the community in a letter to The Fresno Bee, saying that the staff worked with air conditioning specialists throughout the evening to restore cooling. The city is expected to replace the unit with a multimillion-dollar system during the next 15 months, the paper said.