Linda Smith of the U.S. Department of Health and Human Services' Administration for Children and Families said even on a relatively mild day it can be tempting to let a baby sleep while running into the store, but it can be hot enough to kill if a child is left in a closed car even a short time.
"Even on a relatively mild day, temperatures rise quickly in a closed vehicle," Smith said in a statement. "The windows act like a greenhouse, trapping the heat inside, and within 10 minutes can reach life-threatening temperatures."
Smith said it can be deadly hot in 10 minutes even if the outside temperature is only 80 degrees and children age 4 and under are most at risk.
Her agency reminds people, including daycare providers, to be sure they have all the kids out of the vehicle and to, "Look Before You Lock."