Laura Petersen will never forget the day when her granddaughter Kaitlyn died.

A baby sitter left the 6-month-old alone in a van for more than two hours at Lake Mathews in August 2000. Temperatures soared to more than 100 degrees outdoors and 135 degrees inside the vehicle. At a hospital, a doctor told Petersen and her daughter, Tammy Russell, Kaitlyn's mother, that the little girl died.

"I'm seeing it as if it were yesterday ... I still see the doctor's face. It was very difficult. The pain never goes away," Petersen recalled by phone last week. "It's something that no family should experience."

Petersen and Russell created the Corona-based nonprofit organization 4 R Kids Sake to spotlight the dangers of leaving children alone in and around cars. They lobbied for the passage in 2001 of Kaitlyn's Law, which makes it a citable offense in California to leave a child 6 or younger in an automobile without the supervision of someone at least 12 years old.

The group has designated August as Purple Ribbon Month to educate people and has scheduled a special assembly today for students at Foothill Elementary School in Riverside. Representatives from the California Highway Patrol and the Riverside fire and police departments will participate in the event.

Samantha Neathery, a Riverside Fire Department public education specialist, said a 2002 study by San Francisco State University showed that temperatures inside a vehicle can increase rapidly, even with a window cracked open.

Within 10 minutes, temperatures can increase by as much as 19 degrees Fahrenheit inside a car, she said by phone. Within an hour, the temperature inside a car can get up to 123 degrees, even though the outside temperature is only 80 degrees, Neathery said.

Heat stroke occurs when the core body temperature reaches 104 degrees, she said. Death can occur when the body temperature reaches 107 degrees, but children heat up even faster than adults because their bodies' cooling systems are not as efficient, Neathery said.

"Sadly, California is leading the U.S. with heat-related fatalities this year, and we haven't reached the worst of summer heat this year," Petersen said.

Other organizations are pitching in: The Riverside County Sheriff's Department is also participating in Purple Ribbon Month and the Corona City Council presented Russell last week with a proclamation recognizing the awareness campaign.

4 R Kids Sake is planning another school assembly in Murrieta, Petersen said. The date hasn't been set.

Staff writer Melanie Johnson contributed to this report.

Reach Dan Lee at 951-567-2410 or dlee@PE.com