A recent study concluded that extreme heat accelerates the aging of the human body, a worrying fact given the increasing frequency of heat waves due to climate change. The researchers are not talking about the effects of solar radiation on the skin, but biological aging. Unlike chronological age—that answer that you give when asked how old you are—your biological age reflects how well your cells, tissues, and organs are functioning. They then compared people’s biological age with their chronological age, to see how fast their biological clock was ticking relative to their actual age. The results showed that the more extreme heat events people experienced, the faster their biological age accelerated relative to their chronological age.