Summertime, ah beautiful summertime, how I love thee. The time of year when we sweat through a uniform a little faster than usual! Most of us have probably never experienced a serious bout of heat-related illness while on the job, and I’m sure that we’d all like to keep it that way. Yet if your company is anything like the one I work for, you are probably admonished each year around this time to hydrate and be aware of the signs of heat exhaustion and heat stroke. Believe it or not, heat kills more people in the United States each year on average (120 people per year) than any other weather-related cause of fatalities, including floods and tornados.

We often talk about how hot it is going to be — and cringe at the outside work that has to be done when the meteorologist predicts a 90°F-plus day. Interestingly, we rarely consider the equally important relative humidity (R.H.). But we should. Our bodies cool themselves by sweating, a process that requires evaporation to remove the heat stored in the perspiration on our skin. When it’s humid, our bodies can’t cool down as easily because evaporation doesn’t happen as readily. So, to stay informed of when we are most at risk of overheating we need to pay attention to both the air temperature AND the humidity. Fortunately there is a system that conveys just this information, it’s called the heat index.

The heat index, originally dubbed “humiture” (get it?), was created by the National Oceanic and Atmospheric Administration (NOAA) in 1978 with the intent of giving a person a better gauge of how hot it actually felt outside than strictly looking at a thermometer. So, if you are listening to a weather forecast and hear the phrase “but it will feel like” the local media mogul is not just pulling a made up number out of thin air — there is actual science behind it. You may see heat index expressed as a table with temperature values on one axis and R.H. values on the other. If you know both of these numbers and follow them until the row and column meet, you will have the approximate heat index, or what temperature it approximately feels like.

I say “approximate” as there are other factors that will influence the heat index. For instance, if you are working in direct sunlight (as we often do when making exterior applications or checking bait stations), you need to add 15 degrees to the calculated heat index to be accurate. NOAA also color coded its table so you can see how dangerous the various heat indexes are. Of course, you don’t need to carry a table of values around with you like they did in the 70s to stay informed, just pull up a website, like this one,, that displays the heat index for your region of the country.

Naturally, the higher the heat index, the more breaks and water will be needed to stay safe, especially when working in intense conditions like attics or on a bed bug heat treatment. Don’t become a victim like those crispy bed bugs, remember that you are a non-target organism not to be lethally heated! If necessary (and possible), reschedule the work for a cooler time during the day or after the heat spell has subsided, it’s not worth risking your personal safety to kill a few bugs or make an inspection.

Let’s be honest here, if you are going to depart this world there are more noble (and exciting) ways to do it. Being struck by lightning or getting thrown half a mile by a tornado certainly conveys a greater level of machismo and gravitas, but being killed by humiture is just plain not cool! (I hope that’s punny enough to remember!)

The author is manager of education and training at Rose Pest Solutions, Troy, Mich.

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