Every summer, sweltering Americans — myself included — fall for a meteorological scam as we seek information about the day’s oppressive heat.
That’s because the “feels like” or “heat index” measurement blaring from our radios or posted on our weather apps isn’t a measurement at all.
TV meteorologists across the nation trumpet the “heat index” as a headline number, but in fact it’s just a calculated estimate — not something that can be gauged, like air temperature, humidity or barometric pressure.
Its overuse smacks more of sensationalism than scientific clarity, and plays into a destructive narrative of climate hysteria.
The heat index is a formula that did not exist at all until it was developed by the US National Weather Service in 1979.
It combines actual air temperature and relative humidity into an approximate “apparent” temperature — shifting as humidity goes higher or lower.
The NWS heat-index equation attempts to predict the heat that humans perceive, assuming shaded, low-wind conditions and a generic adult body type — ignoring sunlight, wind, individual physiology, hydration, age, weight, health status and multiple other variables.
But it ignores the fact that all individuals experience heat differently: An elderly person or someone with cardiac issues may overheat faster than a young, fit adult, for example.
Weathercasters do us a great disservice by inflating the heat index’s importance and morphing it into a headline-grabbing marketing tool.
Many outlets now forefront the bloated “feels like” temperature while sidestepping the real air temperature that matters for energy use, infrastructure and actual thermal load.
Examples of this behavior are too numerous to count.
WFLA in Tampa, Fla., recently announced an all-time-high heat index figure as the highest “ever recorded.” It wasn’t recorded at all; it was a calculated estimate.
You’re increasingly likely to hear predictions like “today’s high will be 104 degrees!” on a humid day when the real thermometer reads 94 degrees Fahrenheit.
Ginger Zee of “Good Morning America” last month defended her prominent use of the heat index, calling it “the most important number that you need to know.”
“We show heat index because that is what a human feels,” she explained. “If I were forecasting for inanimate objects . . . I would keep it with temperature.”
The problem with over-relying on the heat index is that viewers may think the air temperature is 10 or more degrees hotter than it actually is, making it even more difficult to plan outdoor activities, make clothing choices or calculate heating or cooling needs.
The fact is, sun exposure, wind and metabolic heat production are often more relevant to how you feel on a hot day — important factors for which the heat index does not account.
Worse yet, reporters at outlets such as The Washington Post and Climate Central often seek to link high heat-index values to “climate change.”
But there is no causal link between global climate change and the heat index formula, despite frequent media implications.
Climate change isn’t driving heat-index estimates — city environments are.
We know that urban areas are especially prone to the Urban Heat Island effect, a phenomenon causing cities to be 1 to 7 degrees hotter in the daytime and 2 to 5 degrees warmer at night than surrounding rural zones, due to pavement, buildings, reduced vegetation and anthropogenic heat.
Mapping efforts by the National Oceanic and Atmospheric Administration have recorded UHI hotspots up to 20 degrees hotter.
The UHI effect is not some fringe theory, but a well-documented fact that impacts heat index estimates.
The EPA emphasizes that thermal differences in urban areas amplify heat risk far beyond background climate trends — and points out that heat waves and urban surfaces, not just global temperature, are the leading contributors to heat-related health events.
Lawn irrigation and widespread planting of non-native grasses over the past 50 years have contributed to local humidity rises — boosting heat-index values to the max.
Anytime a forecast touts a “temperature” wildly higher than the recorded official readings from the National Weather Service office, you’re likely being misled.
If broadcast meteorologists want to serve public understanding, they need to start showing the measured air temperature first and labeling the heat index properly, while educating audiences on the differences between them.
Let’s stop pretending calculated “feels like” values are real — and start reporting the actual heat, for real.
Anthony Watts, a senior fellow for environment and climate at The Heartland Institute, operates the award-winning website wattsupwiththat.com.
