The lawsuit, filed by Austin lawyer Jeff Edwards, asks that the temperature at Wallace Pack Unit in Navasota be cooled to at least 88 degrees at all times, not for comfort, but for safety reasons, the Austin American Statesman reported.
The Wallace Pack Unit houses hundreds of geriatric inmates.
Temperatures inside the facility "routinely exceed 100 degrees inside inmate housing areas, threatening the health and welfare of all inmates, especially the elderly, sick and disabled," the lawsuit said.
Inmates are forced to wrap themselves in towels to protect their skin from the burning temperatures of stainless steel tables inside the prison. They often choose to sleep on the concrete floors instead of their metal bunks to cool off, the lawsuit said.
The lawsuit blames 20 deaths in Texas prisons since 1998 on excess heat.
The lawsuit argued the metal exterior walls of the prison's dorms "hold heat like a parked car."
Jason Clark, spokesman for the Texas Department of Criminal Justice said inmates are provided ice, and are allowed to wear shorts and take additional showers during extreme heat. Their outdoor time is also limited.
"Although a detailed cost analysis has not been done, retrofitting facilities with air conditioning would be extremely expensive," he told the Austin American-Statesman.
The lawsuit says the 550 beds in air-conditioned areas of Texas prisons -- reserved for those with serious medical conditions -- aren't enough for the state's 150,000 inmates.
"What we're asking for in this lawsuit is not that the prisons be comfortable or luxurious. What we're asking is that the prisons be humane," said Ranjana Natarajan with the University of Texas Civil Rights Clinic, which along with the Texas Civil Rights Project, joined Edwards in filing the lawsuit.