As a practicing internal medicine physician, I field some version of the same question every time the weather gets hot: Is it safe to be outside right now? This week, the answer leans toward a hard no. The National Integrated Heat Health Information System (NIHHIS) has flagged a dangerous heat wave building across much of the U.S., with major to extreme heat expected through the Fourth of July weekend and beyond.
The temperature on your phone is only half the story. Without also checking the heat index, you are missing the number that actually predicts how hard your body has to work to stay cool, which could be the difference between a good day out and a trip to the emergency room. Here’s how it works, when to worry, and what cools you down.
The U.S. Regions and States Expected to Hit Dangerously High Temperatures
According to the NIHHIS interactive heat map, the central, eastern, and southeastern states are bearing the brunt of this heat wave. Some of the most affected states include: Arizona (particularly in the southwestern part of the state), Texas, southeastern Colorado, Florida, Tennessee, Virginia, and Mississippi. Temperatures are expected to range from the high 90s to the low 100s.
The reason this heat wave is especially brutal: humidity is stacking on top of already-high temperatures, driving the heat index up quickly. This means that elevated temperatures paired with thick, oppressive humidity will push heat indices past 110 degrees Fahrenheit in some spots.
What’s worse, the detail we often miss is what happens overnight. When the lowest temperature for the day stays in the 70s, your body never fully cools off, and a few days of that compounds fast.
The remainder of this article can be read on outsideonline.com.