OKC is 100 degrees this week, but it feels hotter. What's the difference between the temperature and heat index?

Residents around OKC have suffered through triple-digit days all summer, right? According to the records, not exactly.

Oklahoma City has only recorded its first technical 100-degree day on July 25, the National Weather Service reports. Previously, the highest actual temperature experienced in 2023 in the metro area was 98 degrees.

However, meteorologists warn that conditions could turn up the heat index, which would make Oklahoma feel hotter than the new highs we've just experienced.

"We may even see values of 108 factoring in the dew point, especially in central and northern parts of Oklahoma," said National Weather Service meteorologist Jennifer Thompson. "It's been different between drought and dew-point moisture we've seen some range."

Why is the feels-like temperature so much hotter than the actual temperature?

According to meteorologists, both heat and humidity are at play in determining actual temps for the record, and the feels-like temperature.

This is due to the heat index, also known as the apparent temperature, which is the way it feels to the human body when relative humidity is combined with the air temperature, the weather service reports.

When there's less moisture in the air, people tend to sweat more, reports the National Weather Service. The more moisture in the air, the less you can compensate for that with sweat, and the hotter you feel.

This is opposed to a dry-bulb temperature, usually referred to as air temperature, which is the air property that is most commonly used. When people refer to the temperature of the air, they are normally referring to its dry-bulb temperature because the air temperature is indicated by a thermometer not affected by the moisture of the air.

"When there's less moisture in the air, you get less evaporation. You may sweat the same amount but your body cannot regulate the temperature as well because there's less evaporation," said Alex Zwink, a meteorologist with the National Weather Service.

Heat indexes are not officially maintained in National Weather Service records, but with a current dry-bulb temperature matching the year's highest and a heat index of 102 degrees expected, residents should brace themselves for sweltering conditions.

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Why are other parts of Oklahoma hotter than Oklahoma City?

Across the state, triple-digit actual temperatures have already been recorded in the western and northern portions of Oklahoma, including Stillwater and Atoka, Zwink said.

So far, the hottest day for the state was recorded July 13, when Pauls Valley recorded a heat index of 126 degrees.

"It is the most obscene temperature we've observed," Zwink said.

As for why it took so long to reach these temperatures in the city compared to neighbors across Oklahoma and the region, there are more than a few factors at play.

"Will Rogers (World Airport) sits in a valley basically, so accounting for wind direction, elevation, bodies of water and dew point can cause variances, which will make a difference when recording temperature for places in close proximity," Thompson said.

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Historically, observations in Oklahoma have been made at various places, beginning with older sites at Fort Gibson and Fort Towson in 1825 and 1850, respectively. Since 1890, Will Rogers became an official standard bearer for the metro area since 1932, with a Weather Bureau office established to replace the Weather Bureau Observatory on Classen Boulevard.

So far, Oklahoma City's early morning weather has been more on par with Alaska than Arizona, but officials note that our site is an exception and had been among the few in their observation area to miss out on the monstrous numbers.

How much hotter will weather get in Oklahoma City?

With heat indexes expected to reach 105 degrees during the day, keep in mind that National Weather Service heat advisories for the metro or central counties will be in effect until at least 8 p.m., and residents in central, northern and southern parts of Oklahoma should be prepared.

The heat wave is expected to affect those regions more intensely, the weather service reports, while the metro area may experience rising temperatures without a formal advisory.

Adding to the discomfort, the forecast indicates no signs of rain and a wall of pressure keeping the region bone-dry, bringing above-average indexes to Kingfisher and areas along the north of I-40. This prolonged dry spell, coupled with the hotter-than-average temperatures, further intensifies the heat wave's impact.

This article originally appeared on Oklahoman: Temperature vs. feels-like temperature: What's the difference?