Heat waves are becoming more intense. What will it mean for people and places?

Heat waves can cause adverse health effects and even be fatal. How are people and cities preparing for a world with more extreme heat?

In early summer, large swaths of the U.S. were hit by an extreme heat wave which caused temperatures to reach into the upper 90s in some parts of the Midwest and Northeast. 2023 was the hottest year on record, and this year is on track to break that record again. As higher temperatures and extreme heat waves become more common, heat-related risks are only going to get worse.

Umair Irfan, a correspondent at Vox, wrote about the rippling effects of more extreme heat waves. He joined “Marketplace” host Kristin Schwab to talk about his reporting. Below is an edited transcript of their conversation.

Kristin Schwab: Well, let’s start with the basics. What is a heat wave?

Umair Irfan: A heat wave is defined typically as the temperatures that are in the 90th percentile or higher for a given region. So, what that means is that the threshold for a heat wave changes depending on where you are. The temperatures that are required to be considered a heatwave in Phoenix, Arizona are going to be much higher than the temperatures that will be considered a heatwave in Portland, Oregon. But that sustained temperature in the 90th percentile, that’s the wave part of the heatwave.

Schwab: And you in their story talks about how there’s actually less relief happening at night that heat waves kind of continue on in the evening. Right.

Irfan: So one of the distinct signals we’re seeing in recent years is that temperatures are not cooling off as much at night as they used to and that has really important health consequences. Because one of the ways that we cope with extreme heat is finding relief in the evening time and at nighttime. And that means that the effects of heat accumulate faster in people over a period of time.

Schwab: You write about some of those health risks, some very direct and some pretty indirect. What are some of those odd health effects?

Irfan: Right, we find out that heat influences our body in a lot of direct and indirect ways. Some of the indirect ways are things like how heat influences our medications. There are a lot of drugs that are actually less effective when temperatures go up, and there are also a lot of medicines that make us more vulnerable to extreme heat, so things like diuretics, things like blood pressure drugs. And then of course, there are the direct effects of extreme heat, just simply being dehydrated, hyperthermia, where your body temperature accumulates to a dangerously high temperature, all those things are at play when we see temperatures rising.

Schwab: There is of course, the economic piece of this too, not just for households, but also cities. What are cities doing to counteract this?

Irfan: At a large scale, I mean, I think the big public health thing is to generate awareness to make sure that people understand the risks of extreme heat, how to understand their own vulnerabilities, and then the precautions that they should be proactive about taking. As far as trying to stay cool, we find that urban areas tend to accumulate heat faster at higher levels than surrounding rural areas. This is a phenomenon known as the urban heat island effect. And so some cities are working on ways to try to mitigate that with things like tree cover. And then also things like, you know, being more energy efficient with how we use things like air conditioning. One of the ways that air conditioning works is that they reject heat outdoors. And so, while it cools off an indoor space, it can heat up an outdoor space. And so being more thoughtful about how we generate electricity and how we use electricity, and how we condition our indoor spaces are all things that we can do to help reduce the overall impact of heat.

Schwab: So, I’m wondering if last year was the hottest year on record and this year is set to surpass that, is there a way that things can get better?

Irfan: In a few ways, yes. One is that we can reduce our overall exposure to the heat by understanding the risks that we face and then taking steps to mitigate them. You know, in the United States, for instance, there is right now no federal workplace heat safety standard. Right now, workplaces are pretty late to the game as far as mitigating and reducing the harms from heat. And we’re not just talking about people who work outdoors and construction site or farm workers who are you know, very vulnerable, but people who work in warehouses, delivery workers, and even people who work in kitchens. There’s a lot we can be doing to reduce their exposure. And then in terms of the overall big picture on a planetary level that we can be doing, obviously, there’s the big one is to reduce our impact on the climate. That’s to reduce our greenhouse gas emissions over time to mitigate the rate of warming. And then in more intermediate term, there are things that we can be doing as far as how we design our cities to have more green spaces and more reflective surfaces, and that can also help reduce some of these risks from extreme heat.