In many parts of the world heat waves are happening more often with greater intensity and for longer durations. By 2050, Earth’s mid-latitudes could be experiencing extreme heat between 90 and 180 days a year, with tropical regions enduring even more. So how hot is too hot, and what can people do to handle the heat? Carolyn Beans digs into how heat waves affect your body. Lesson by Carolyn Beans, directed by Reza Riahi.