Three of the five athletes were transported to an area hospital, and two were treated by paramedics at the scene.
The event was the final cross-country meet for the Empire League. Hundreds of students were gathered from various Orange County schools to participate in the meet.
The first call went into the fire department around 3 p.m. with reports of a teenager needing assistance due to a heat-related illness. Just 20 minutes later, another student was having problems
The course is very hilly and considered very difficult even on a normal day. The extreme heat was just too much for some students.
"It's just been really hot. A lot of kids are out there are running their tushes off," said assistant coach Keith Martyn. "I've never seen anything like it. About five kids are being taken away in ambulances, and it's just not a good day to be a coach."
Another coach said under-hydrating or over-exertion may be partly to blame for the illnesses.
In Santa Ana, temps reached 100 degrees, trumping a 1949 record of 98 degrees. The heat reached 100 at John Wayne Airport as well, breaking a 2009 record of 79 degrees.