Of course, it's always hotter in summer. But the heat waves today are not the same as those 60 years ago. The warming climate is making heat waves more intense and they are lasting longer too.
When high temperatures stick around for such prolonged periods in places that are used to such sweltering weather, risks increase for both humans and the infrastructure meant to support them.
Climate experts and meteorologists are concerned that these "heat domes" will continue to become more common as the Earth heats up.
Even now, about 700 people in the U.S. die each year from heat-related exposure, according to the Centers for Disease Control and Prevention.
So it's important for people to keep cool and protect themselves from the extreme heat.
To get a sense of how to do that and what to look for, NPR's All Things Considered spoke with Kristina Dahl, a senior climate scientist with the Union of Concerned Scientists, about which groups are most at risk, the early symptoms of heat-related illness and what cities and individuals can do to mitigate the risks.
Who is most at risk?
Older adults tend to be most at risk for heat exposure, Dahl says.
"As you become older, your body has more trouble regulating your temperature, and so adults have a harder time shedding the heat that accumulates in their bodies when it's extremely hot outside," she says.
Athletes are also at high risk for heat-related illnesses.
"Often when we are young and healthy and strong, it's harder to listen to those early signals of heat illness that your body's trying to give you," Dahl says. "And so we do, unfortunately, every year see people who are otherwise fit and healthy passing away due to extreme heat exposure because they're exerting themselves outside and not taking those precautions of reducing their exercise and staying indoors and keeping cool."
If you are experiencing early symptoms of heat-related illness, it's important to rest and hydrate.
What are the symptoms to watch for?
Dizziness, headaches or extreme tiredness are some of the early symptoms of heat illness, including heatstroke and heat exhaustion.
Dahl says if you're experiencing any of those symptoms, regardless of age, it's important to pause and stop what you're doing.
"Make sure you take some time to lie down and rest, drink water and if you can, get to a cool place," she says. "So for some people that's their air-conditioned home or apartment; for other people that might mean needing to go someplace like a public library that might be opening up as a cooling shelter in your community."
If your body temperature reaches 103 or higher, you could be experiencing a heatstroke, which is a medical emergency that requires immediate attention. According to the CDC, you should call 911, move the person experiencing heatstroke to a cooler place and try to lower the temperature by applying cool washcloths or placing the person in a cool bath. You should not give them anything to drink.
How can you look out for yourself and others?
Pay attention and don't push past or ignore the early symptoms.
"It can be easy to overlook if you're say out there mowing the lawn and you've only got the last few rows of the lawn to go before it's done, or you're just 10 minutes away from the end of your football practice," Dahl says. "But it's really important if you're starting to feel those symptoms to get some rest, to hydrate and to cool off."
If you're not an older person, it's important to check on your neighbors and relatives who are.
"[Make] sure that they have the opportunity to cool off," Dahl says, "that they're not sitting [in] a hot house all day without an air-conditioning unit, without a fan, without the ability to get to a place like a cooling center."
How does the heat index come into play?
When it comes to the body's experience of heat, temperature is only one component, Dahl says. Humidity is another important factor.
"As the humidity rises, it becomes harder for the sweat to evaporate off of our skin, and it's that evaporative effect that allows us to cool our bodies," Dahl says. "The heat index is a combination of temperature and humidity. It's often called the 'feels like' temperature because when it's more humid, it feels hotter to our bodies and our bodies experience the temperature as being hotter."
If you live in an area where humidity is an issue, Dahl says, be sure to look at the heat index and not just the temperature.
What can employers and cities do?
People who have jobs that require them to be outdoors should be aware and cognizant of early signs of heatstroke, but Dahl says their employers also have a responsibility to address the risks.
"The onus is also on employers to be providing adequate hydration breaks, rest breaks, shade, cooling, maybe even shifting work hours to earlier, cooler times of the day," Dahl says. "We can't put all of the onus on the workers themselves because often the work is designed in ways that disincentivize taking breaks."
That applies to agricultural workers, for example, who might not be inclined to spend a lot of time cooling down if they're paid based on the amount of fruit they've harvested during their shift.
Cities can get hotter than surrounding areas because of the amount of concrete and the lack of trees and more natural land cover. But local governments can play a part in reducing this urban heat island effect.
"Things like planting shade trees is an incredibly effective measure," Dahl says. "There are also programs to paint rooftops white, and that helps to reflect heat away from the urban land surfaces so that the buildings retain less heat and people are able to stay cooler."
NPR's Wynne Davis adapted this interview for the web.
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