It’s not “like 90% humidity” outside, but that doesn’t mean it isn’t muggy

Posted at 9:51 PM, Jul 09, 2015
and last updated 2015-07-09 21:51:58-04

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Many times during the summer, you may hear someone say “there’s like 90% humidity outside!”, but this simply isn’t true. It’s difficult for the relative humidity to even get above 50% on a hot day, but that doesn’t mean at all that it’s not humid.

Relative humidity is calculated by comparing how close the dew point temperature is to the actual temperature. On an average summer day with a temperature of 95 and a dew point of 75, the relative humidity is only 53%.

Unfortunately, our bodies feel the dew point, not the relative humidity.

Even though the relative humidity is low, those dew points in the 70s are brutal because they prevent the sweat from evaporating off of people’s skin, which is the body’s primary way of cooling down. This is where the “heat index” value comes into play.

All math aside, the bottom line is that relative humidity is lower during the heat of the day, but it still feels just as humid to us.

Remember to stay updated on the heat and humidity on News Channel 3 and on our VIPIR app.

–Andrew Green