Category: meteorology

meteorologyScience

“It’s not the heat…

…it’s the humidi…oof….OW! HEY, CUT IT OUT!

Sorry. Had to be done. But c’mon, admit it. There are few phrases more annoying than “It’s not the heat, it’s the humidity” (ed. note: Number one: “Looks like somebody has a case of the Mondays”). But with about one in three Americans in the middle of a heat wave, maybe these people are on to something.

The National Weather Service (ed. note: Apparently, they don’t make and deliver the weather, so we recommend “The National Weather Forecast Gang”) warns that most of the northeast and midwest US will be experiencing a heat wave right up until July 4th holiday. Alarmingly, reports of high temperatures plus high humidity will mean reading of over 100 on the heat index.

Wait. What in the name of my broiled sunburn is the heat index? So, answer – What is the heat index and do we care? Well, like most things there’s a short answer and a long answer. The short answer is “it’s how hot it is, and no, you really don’t care much beyond ‘f*ck, it’s hot’, do you?” The long answer is still pretty interesting. All the heat index represents is how hot it FEELS. Think wind chill, but with less wind and definitely less chill.

This chart, handily provided by the good people at NOAA, shows that basically, the more humidity you add to higher temperatures, the more it feel like three rats getting intimate in a wool sock (ed. note: Hot and unpleasant. Especially for the third rat. He’s always left out).

heat index

Note the density of orange and red in the chart. Red and orange never mean good things on a chart; this applies especially to a chart of Starburst flavors (ed. note: Yellow rules. Fight me if you disagree). It also means that if its above 90 degrees (that’s in freedom units…works out to 32 centigrade) and it’s humid, you’re gonna have a bad time. Except this bad time means your dog and/or elderly relative might die of heat stroke.

OK, great. We have a chart that tells us when the outside feels like sitting in a fat man’s armpit. But, I can hear you thinking is there a handy equation I can use to calculate the heat index? No. There most assuredly is not. There IS an equation, but handy it ain’t. Here it is (where T = Temp in Fahrenheit and R = Relative humidity):

Heat Index = -42.379 + 2.04901523T + 10.14333127R – 0.22475541TR – 6.83783 x 10-3T2 – 5.481717 x 10-2R2 + 1.22874 x 10-3T2R + 8.5282 x 10-4TR2 – 1.99 x 10-6T2R

Good lord, that certainly doesn’t help. So, what the heat index tells us, despite the obvious (it’s hot) and its cumbersome math is that prolonged exposure to a mix of high temps and humidity can have a seriously deleterious effect on people and pets (ed. note: this means you can get heat exhaustion or the much more serious heat stroke). A high temp one day can be more or less dangerous than the same temp the following week. Take the right precautions; such as:

  • Hydrate. Lots
  • Light weight, loose clothing
  • Hydrate. That means water, not margaritas, which despite being delicious aren’t helpful here
  • Wear a hat. And would it kill you to wear some sunscreen?
  • Alternate sun time with cooling down in the shade time

And the next time some slack-jawed doofus tries to tell you that it isn’t the heat, it’s the humidity, you can tell them no, it’s actually the heat index. And then you can show them the above equation and then beat them to death with a shovel.