When I was growing up in New England winters, there was the temperature and then there was "wind chill." Temperature was pretty much irrelevant. Wind chill was the important number, since that was what you were going to experience when you walked out the door.
Fast forward to summertime in the DC area, where the humidity is tactile: a hot washcloth pressed over the nose and mouth, a dog’s hot breath in your ear, a damp velvet suit hugging your every move. The humidity and heat combine to create the yang to wind chill’s yin – the heat index.
The heat index is on us, with expectations of heat experiences of over 100 degrees, and even with jogging in the morning before the full blast of summer, I tell you I am melting .