BATON ROUGE — July is quickly turning to August, with no real break from the heat in sight and extreme heat warnings in effect. State Climatologist Jay Grymes explains what’s causing the hot July days to feel even hotter.
Louisiana isn’t the only state dealing with what feels like excessively hot temperatures. On July 26, the U.S. Department of Energy (DOE) issued an emergency order to keep 17 states, including Louisiana, powered during the region’s energy emergency from hot weather conditions.
The order directs the Southwest Power Pool, Inc. (SPP) to use specified backup generation units and to order their operation as needed to maintain reliability. The DOE estimates more than 35 gigawatts (GW) of unused backup generation remain available nationwide.
For Louisiana and other nearby states, a high-pressure ridge or “heat dome” is what’s keeping the weather hot with little relief. The drier weather is accentuated by this heat dome, which acts like a lid on the atmosphere, Grymes explained. This keeps clouds from building vertically, which is necessary for rain.
“We’ve got to have vertically building clouds in the summer to get our typical rain showers and thunder showers, and if you’ve been kind of looking at the sky in the afternoon the last couple of days, it’s not necessarily that it’s been cloud-free, but the clouds just haven’t gotten very tall. And if they don’t get tall, they’re not going to produce rain,” he said.
In addition to the clouds not being able to build up vertically, this high-pressure ridge allows more sunshine to get through, Grymes said.
“Don’t provide any clouds, you get more sunshine. You get more heat buildup. The afternoon just gets hotter and hotter. And then factor in our humidity, which has been a little bit above normal—well, the humidity actually makes it feel markedly more uncomfortable.
“90 degrees is hot, no matter how you slice it. But 90 degrees with Louisiana humidity starts to get into that very uncomfortable range very, very quickly.”
The humidity is what’s making the “feels-like temperatures” in excess of 105 degrees, even when the actual temperature is in the upper 90s. The National Weather Service has issued “Extreme Heat Warnings” (formerly known as Excessive Heat Warnings) in several parishes this week, with the rest of Louisiana experiencing heat advisories.
“We may get away from these extreme heat warnings, which are kind of the the top shelf of heat alerts that the NWS can put out, soon, but let’s face it: the difference between ‘it feels like 108’ and ‘it feels like 113’ is not all that big. I mean, they’re both impressively hot, and it’s really more about how much time you spend it than it is the actual number itself,” Grymes shared.
The heat index refers to the “feels like” temperature in the shade with low activity level, he added. So, spending time in direct sunshine can add another 5-10, or even 12-15 degrees to the “feels like” temperature.
Even when the sun goes down in the evening, temperatures are staying fairly warm overnight. Grymes explained that the humidity is much of what is to blame for the nights staying warm and uncomfortable.
“But as the air gets warmer, it tends to have the ability to hold more moisture. The more moisture that the air holds, the more heat that it will hold, even after the sun sets. So humid air tends to stay warmer longer than drier air, and so when you have higher humidity, the overnight lows tend to take more time to drop,” he said. With early sunrise, there’s not much time before it’s back to feeling hot.
“We won’t get a prolonged break from this summer heat until the latter half of September, heading into October. But the the outlook for the rest of the summer does call for temperatures to stay on the warm side, so don’t be expecting any real breaks—certainly not any significant breaks—anytime soon.”
With no true relief from the heat coming before the fall, Grymes said it’s important that people take precautions when they can to avoid becoming dangerously hot such as limiting exposure to daytime heat. If you’re outside working in your yard or on a project, take frequent breaks and split up the job. Grymes suggests taking breaks to go indoors, cool your body temperature and re-hydrate before going back outside.
“Do it in pieces so that you go inside, bring your body temperature down just a little bit, so that you don’t slip into that state of discomfort that suddenly leads into heat exhaustion or heat stress, because that’s when you start getting the dizzies; that’s when you start getting the upset stomach. And in this kind of heat, heat stroke is very possible.”
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