Whoosh! There went $24.

But before Laura Petersen could chide her grandchildren, she heard 7-year-old Kristen Russell say, "Catch your balloon, Kaitlyn." Her 9-year-old brother, Derek, quickly added, "Catch mine, too."

Kaitlyn is the baby sister Kristen and Derek knew for just six months. The child died in August 2000 when her babysitter left her stranded in her sweltering minivan while visiting a friend in a Lake Mathews neighborhood.

Each August, Petersen and Kaitlyn's mother, Tammy Russell, fire off information pamphlets and thousands of purple ribbons to educate people about the dangers of leaving children unattended inside cars. Heat-related fatalities can occur in any month, but summer months are especially tragic.

On Friday morning, Corona schoolchildren will launch balloons with purple ribbons attached.

Just this week, four children in four separate states died of hyperthermia-suspected causes, according to the Web site of 4 R Kids Sake, the nonprofit organization Petersen and Russell started after Kaitlyn's death. Russell is appearing today on "The Early Show" on CBS at about 8:05 a.m.

Petersen uses the Internet to search for such fatalities every day. The keywords she uses include: "child," "toddler," "hot car," "SUV," "truck," "heat," "hyperthermia" and "died."

She said she hopes she never gets any hits. But, she's posted on the Web site information about 15 heat-related deaths in the past six weeks. Kaitlyn's death sparked one state legislator to propose a bill making it unlawful to leave a child unattended in a vehicle.

Corona Fire Chief Michael Warren praised the grass-roots efforts of 4 R Kids Sake and said he believes the group is making a difference. "Out of a tragedy, we've seen goodness," he said Wednesday by telephone.

He said his agency is seeing fewer incidents related to children left in cars -- but it hasn't stopped. His department has responded to six such cases this year. Within minutes, the inside of a car can reach deadly temperatures of 120 degrees and higher.

Bay Area meteorologist Jan Null researched hyperthermia, and his study is published in this month's issue of Pediatrics.

Paul Alvarez / The Press Enterprise Laura Petersen of Corona plans to distribute purple ribbons during August as a reminder not to leave children in cars unattended.

"We know when the body's temperature hits 104 degrees, heat stroke can happen; we can have unconsciousness, delirium, profuse sweating," Null said by telephone from Oregon, where he was testifying as an expert witness in a criminal trial pertaining to a child's heat-related death.

"We know at 107 degrees cells begin to die, organs start shutting down, people start dying."

Inland law enforcement officials and firefighters recognized Purple Ribbon Month early in the campaign. Now, the California Highway Patrol recognizes it statewide.

Three CHP officers dropped by Petersen's Corona home Tuesday morning to pick up boxes of purple ribbons. Officers will tie the ribbons to the antennas of their patrol and motorcycle units and display them during August. Other volunteers will wrap larger ribbons around trees.

"We believe every ribbon we tie might save a child's life," Petersen said at her home after the officers left.

The color symbolizes Kaitlyn's February birthstone. She would be 5 now. Attending kindergarten. Finger painting. Playing with her older siblings.

On the first Christmas after his sister's death, Derek surprised the adults with his wish from Santa Claus. "He said he wanted a pair of wings," Petersen remembered. "He said, 'So I can fly up to heaven and bring Kaitlyn back and make everyone happy again.'"