News outlets report 62-year-old Leimome Cheeks was charged with two counts of child endangerment.
Cell phone video shows a girl getting out of a kennel from the back of an SUV.
According to a Memphis police affidavit, Cheeks says there was no room inside her vehicle Saturday, so she told her grandchildren -- ages 7 and 8 -- to get inside the kennels.
There were no air conditioning vents in the back of the vehicle and the children told police they became hot. Temperatures in the area reached about 95 degrees Fahrenheit.
Cheeks was being held Sunday in the Shelby County Jail.
Jail records didn't indicate whether Cheeks has an attorney who can comment on the charges.
The Associated Press contributed to this report.