LOUISVILLE, Ky. — Kentuckiana is sweltering during the hottest week of the year.
Daytime temperatures nearing 100 degrees, and heat index values up to 110 degrees make it extremely uncomfortable outside - meaning indoor air conditioning is a great relief.
However, not everyone has access to working A/C, making the heat even more dangerous, especially at night.
Dr. Clara Sears of the University of Louisville says urban heat islands in areas such as Louisville make the nighttime temperatures worse.
"When there's more concrete outside, we have an urban heat island here. So it impacts the ability of the city to cool in the evening. So those nighttime temperatures tend to be higher."
This is especially true in Louisville's West and South Ends which has some of the lowest tree canopy in the city. Overall, Louisville has one of the worst urban heat islands in the United States because of its dwindling tree canopy.
The urban heat island is a phenomena found in major metropolitan areas. The abundance of concrete and asphalt absorbs solar radiation much more efficiently than vegetation, and is very slow to release it at night. This artificially inflates temperatures.
More trees would help this problem.
"If greening cools the neighborhoods or keeps temperatures from getting too high at night, it's hypothesized that that could improve sleep and then also result in better cardiovascular health," Dr. Sears says.
As for the human impact, UofL's Dr. Aruni Bhatnagar says cardiovascular health is most sensitive during intense heatwaves.
"What happens when you sleep is that your core body temperature needs to drop. So you need to cool down the inside."
Sudden jumps in temperatures similar to what we experienced with this heatwave strain the body much more compared to a gradual warm up. The elderly, very young, or those with pre-existing diseases are most vulnerable.
Heat is the number one weather related killer in the United States.
"Most of the fatalities associated with heat waves are due to cardiovascular reasons, right, and people who are already susceptible, most of these happen in the early morning hours, just before getting up or just after getting up," Dr. Bhatnagar says. "And the reason for that is that when you go to sleep, then when you get up there is a surge in your excitatory stimulus."
In high temperatures like this, air conditioning is the best "medicine" for staying healthy, but if a working A/C isn't available, there are other options.
Run a fan to circulate air, don't sleep under many layers, and have a shower before bed to help lower your body temperature. It'll not only help you sleep better, but keep you healthier during extreme heat like this.
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