Some are crude, and useful only for quick estimates, and others are more sophisticated, using multiple variables to generate a measurement for subjective experience. Each has a niche where it performs better than the others, but none are perfect. To date, there have been over 100 different systems of measurement developed to measure how people experience temperature. Based on these meteorologists' expertise, Steinberg says he and his co-authors adjusted things locally. Other AccuWeather meteorologists, he says, felt like certain geographic areas and conditions altered perceived temperature in ways that couldn't be measured through data collection. But even with physics, observed data, and surveys, Steinberg admits some estimation went into RealFeel. To calibrate their model to what people actually feel, Steinberg and his colleagues ran RealFeel through a gauntlet of user surveys, and adjusted the algorithms accordingly. "What we did was assume an average person in terms of body size and physical capability, and we also assumed they were dressed appropriately for the weather," he said.
But external conditions aren't the only thing that determines how people feel temperature. Combining the two is one of the easiest ways to determine perceived temperature, and this is basically how Feels Like temperatures are calculated.
Second, they both proved that you needed more than weather data to do so. Wind chill and the heat index showed meteorologists two things: First, it was possible to quantify the way people experience weather. Humans regulate their temperature by sweating, and we have a hard time doing so if the air is already sticky with moisture. The higher the dew point, the more humid the air. When the temperature drops far enough-called the dew point-the air particles become too densely packed to store any more vapor, so it starts to condense on solid surfaces. The cooler air gets, the less water vapor it can hold. The percentage of water vapor in a given volume of air is called its humidity.
Air always has some amount of water vapor. In 1978, a researcher named George Winterling developed the heat index in an attempt to codify this correlation. Like wind and chill, humidity had a long anecdotal correlation with heat. This ended up being too simplistic however, and eventually had to be amended with data that accounted for human factors like body type, clothing, and activity.Ī few decades later, other researchers tried to measure perceived temperature in the other direction. Using plastic vials of water in a variety of wind and temperature combinations, they eventually published a table where you could get perceived temperature by cross referencing one reading from a thermometer and another from an anenometer. However, nobody had assigned a number to this feeling until the mid-1940s, when two Antarctic explorers observed that the wind actually caused water to freeze at higher than normal temperatures. For instance, we all instinctively know that a stiff wind will make the air feel cooler. Measuring how humans experience temperature isn't new. But can the AccuWeather, the Weather Channel, or even Al Roker know you like that? What is the methodology behind this meteorologic metric? Whatever it's called, this number purports to tell you how the air outside will feel against your skin. AccuWeather's proprietary formula is called RealFeel, and other stations use a similar metric called Feels Like. Most weather reports include a metric that supposedly tells you the same thing. My sense of the weather comes by combining data from the morning's report-temperature, along with humidity, wind speed, and precipitation-with accumulated experience. I've moved a lot, and a city never feels like home until I can anticipate how the day's weather will feel.
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