The Twin Cities tied its record high temperature yesterday at 97 degrees Fahrenheit. However, the winds blew strong with air at a dew point in the low 60s, which made the heat relatively tolerable. After spending most of August at our second home in southwest Florida (leaving there just as Hurricane Idalia hit), my wife and I got acclimated to a far more uncomfortable daily combination of heat and humidity.
Before departing for Minnesota, I set up a SensorPush to monitor temperature, humidity and dew point—the temperature at which air becomes saturated with water vapor. I want to be on guard for the air conditioning going out. If that happens in Florida homes, mold can grow. After experiencing this once (due to renters not running the A/C) and dealing with an expensive remediation, I am keen to prevent another episode.
Closely related to dew point is the wet-bulb temperature, which, as chemical engineer, I learned how to measure with a sling psychrometer. The wet-bulb-temperature can then be converted to relative humidity.
To prevent heat-related deaths in training camps, the US military developed a more sophisticated measure called the wet bulb globe temperature (WBGT). It provides a good measure for the advisability of being active in full sun. The Texas University Interscholastic League requires that outdoor practices be shut down if WGBT exceeds 92.
“As with all indices that integrate elements of the thermal environment, interpretation of the observed levels of WBGT requires careful evaluation of people’s activity, clothing, and many other factors, all of which can introduce large errors into any predictions of adverse effects.”
– Grahame M Budd, Wet-bulb globe temperature (WBGT)–its history and its limitations
Other measures use to gauge comfort are Heat Index and Feels Like Temperature (FLT). I like the FLT because it accounts for the benefits of evaporative cooling. For example, as I write this, the actual temperature is 95 degrees and the FLT is only slightly higher at 96.
I’m getting too hot and bothered with all these measurements to continue much longer, but here’s yet another approach used by AccuWeather—the RealFeel Temperature.
What really matters is how you feel and what can be done to avoid discomfort. For example, earlier this summer I went to our Minnesota’s Washington County Fair on a very hot day and stopped in at a beer garden for a cold brew. However, I soon realized that its hot tin roof radiated heat down to the picnic tables—overcoming any advantage to being in the shade.
Sometimes you can find no relief other than hunkering down in an air-conditioned area. How did we ever get by without it?