The Contra Costa County Fire Protection District received a call just before 10 a.m. on a report that someone had fainted at the Heritage High School graduation, a fire dispatcher said.
When fire officials arrived at the school, located at 101 American Ave., they had to treat additional patients who were dehydrated from the scorching temperatures, according to the dispatcher.
Several patients were transferred to local hospitals for further treatment. Fire crews left the high school at 1 p.m.
The Class of 2013 graduation ceremony was scheduled to begin at 9:30 a.m. and end at 11 a.m., according to the school's website. Stadium doors were scheduled to open at 8:30 a.m.
The National Weather Service predicts a high of 107 in Brentwood today.