In 2013, California State Pelican Bay Prison employed hypothermic punishment as witnessed by this Reuters article, here is a snippet:

"They are the upping the ante in terms of cold. It's clearly a tactic to make everything uncomfortable and in essence retaliate for the hunger strike," civil rights attorney Anne Weills told the Guardian after a recent visit to Pelican Bay. "They are freezing, these men. I could see them shivering in front of me. I had two sweaters on and I was freezing."

"They are suffering," she said. "This puts them at risk of hypothermia."

Reuters Article Titled: Inmates claim prison guards are retaliating against hunger-strikers in California.