Meet the wet bulb globe temperature, the ominous measure that shows when it's too hot to go outside. https://www.wired.com/story/why-its-almost-too-hot-to-play-tennis-at-the-french-open-2026/?utm_brand=wired-science&utm_campaign=aud-dev&utm_medium=social&utm_social-type=owned&utm_source=voante-science