Heat and humidity make 'Tokyo Summer the worst in the history of Olympics'

Japan's summers are hot, humid, and can be deadly. If records are being broken during events at the Olympics, Tokyo 2020 could also emerge with perhaps a record it wouldn't have wanted.

Before the pandemic, heat stroke was the biggest risk to athletes for the Tokyo Olympics, but during the first week of the Games the heat has been compounded by humidity values ranging from 66 to 84%, making it feel much hotter, and limiting the body's ability to cool down through sweat and evaporation. "When you take into account not only the temperature, but also humidity, I would say that a Tokyo Summer is the worst in the history of Olympics," says Makoto Yokohari, professor of environment and urban planning at the University of Tokyo and adviser to Tokyo 2020, who spoke to CNN before the Games started.