Texas says no inmates have died due to stifling heat in its prisons since 2012. Some data may suggest otherwise.

Austin, Texas — A heat wave that has consistently pushed temperatures well above 100 degrees across much of Texas this summer had family members of inmates on Tuesday calling for lawmakers to ensure that all of the state's prisons are fully air conditioned.

"They're cooking our inmates in the Texas prison system," said Tona Southards Naranjo, who believes the death last month of her son, Jon Southards, was caused by excessive heat in his prison, the Estelle Unit in Huntsville. Naranjo was one of more than 60 people who attended a rally outside the Texas Capitol on Tuesday.

Advocates and others have been highly critical of the lack of air conditioning in the nation's largest prison system, alleging temperatures that often go past 120 degrees Fahrenheit (48.9 degrees Celsius) inside Texas prisons in the summer have been responsible for hundreds of inmate deaths in recent years.