This year, the hottest July ever was recorded — and parts of the country were hit with heat waves that lasted for weeks. Heat is becoming increasingly lethal as climate change causes more extreme heat. So in today's encore episode, we're exploring heat. NPR climate correspondent Lauren Sommer talks with Short Wave host Regina G. Barber about how the human body copes with extended extreme heat and how today's heat warning systems could better protect the public. If you can, stay cool out there this Labor Day, dear Short Wavers.What science story do you want to hear next on Short Wave? Email us at shortwave@npr.org.