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A Hazy Connection Between Hot Weather And Crime

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When temperatures rise, the conventional wisdom goes, so do crime rates. Wired examined what science has to say about the connection between heat and crime. Their finding: "The answer... is hazy and hotly contested." Wired's Brandon Keim explains the study.

TONY COX, host: Well, the heat wave hasn't let up in many regions across the nation. Oklahoma and Texas are getting scorched by multiple days of triple-digit temps. And as conventional wisdom goes, when the temperature rises, so does the crime rate. Wired magazine recently examined what science has to say about any connection between heat and crime. Their finding, quote, "The answer is hazy and hotly contested," end quote.

We'd like to hear from those in law enforcement in our audience. What kind of activity do you see in hot weather, and how does it differ from crime in colder times? 800-989-8255 is the number to dial. Our email address is And you can join the conversation at our website. Go to and click on TALK OF THE NATION.

Joining us now from his home in Bangor, Maine, is Brandon Keim. He is a science reporter for Wired magazine. Brandon, nice to have you. Brandon? Hello, Brandon. You there?


COX: There you are. There you are. OK. The heat. It was the heat, Brandon. That's what it was. It was the heat.


KEIM: It must be.

COX: What does science tell us about heat and crime?

KEIM: Well, it's complicated. In general, crime rates do go up when it's hot, and there have been many studies that have shown that. But then the question is, so why is that? And there's a number of different explanations, or proposed explanations. One is that it's just a matter of convenience. When the temperature goes up, the weather is nicer. Everybody goes outside and they stay out and they drink and they have fun and socialize and do all the things that make assaults mathematically more likely.

But there's also psychological explanations. And the notion - there's a couple of different explanations. But one is that just heat makes us more prone to violence. There's just something about it...

COX: Why? Why? Why?

KEIM: It stresses us out. It sort of causes these physiological changes that track with fight-or-flight responses. In, you know, clinical - in laboratory settings, you can turn the temperature up, and people will actually be less likely to condemn violence, more likely to condone it. They'll be more likely to see a neutral expression and think that it's hostile. There's just sort of lots of, you know, sort of evidence that indicates, you know, what we intuitively think, because, of course, heat and violence is reflected in our language. You know, tempers flare, angers simmer. And then when we calm down...

COX: Yeah, boiling...

KEIM: When we cool down.

COX: Yeah, cooling down. Let me ask you this because part of your reporting talks about the fact that there really is not a consensus with regard to the relationship between heat and crime, and that - and at least in one of the studies that are - that is mentioned in your article, there is a contrary viewpoint. What is that?

KEIM: Well, the contrary viewpoint is that, yes, crime does go up with heat, but only to a certain point. And the study that you mentioned - it's this very large and significant one that was conducted - it's an analysis of crimes in Minneapolis, Minnesota, over two years in the late 1980s. And there is one interpretation of the numbers, which showed that, you know, yes, crime and heat went up together, but only to about 85 degrees, and then they started to drop back down again.

And there's a couple of different possibilities for that. One, like I mentioned earlier, you know, people go out and interact when it's warm. But then it gets so hot we all just stay inside with the air-conditioner on and don't assault anything. And the other is that, actually, discomfort sort of induces these competing tendencies of aggression and escape, and aggression wins out up until we get so uncomfortable that we just want to flee. So both of those would suggest that, yeah, when it's not 85 degrees, crime rates are - assault rates drop. And the researchers supported the idea of, you know, social interaction and so-called opportunities for violence. But then there is another group of researchers who looked at this and said, hey, wait a second. You're reading these numbers wrong. Actually, they continue to go pretty much straight up, all the way up to 95 degrees. And their interpretation fits more with the notion that heat just makes us angry and...

COX: This is TALK OF THE NATION, if you're just tuning in. We are talking about heat and crime and the connection between the two, if there is one. Our guest is Brandon Keim. He is a science reporter for Wired magazine, a freelance journalist who wrote the article the "The Hazy Science of Hot Weather and Violence." We'd like to know if - especially from those of you in the audience who are in law enforcement, what has been your experience with regard to heat and crime? Does it go up where you work when it's hotter? And does it go down when it's colder and why? And what are some of the stories you can share with us? Our phone number here in Washington, 800-989-8255. The email address is

Now, Brandon, I know that you're not a scientist and that you are a freelance writer, so this question may be beyond what you're able to answer, but I'll throw it out anyway. If the theory that heat and crime are related is true, then it would suggest, would it not, that places like Texas, Oklahoma, Florida, Arizona, Nevada would be places where there would be a lot more crime because it's hot there all the time?

KEIM: Broadly speaking, that is true. Although I'm sure a statistician of crime would come in and say, well, there could be all these different caveats, and you could have a lower intrinsic crime rate in the South, which is actually raised when it's hot, or vice versa. But as a rule, if true, there does tend to be more violence in warmer climes.

COX: Let's talk to Steve from Visalia - actually, Steve, hold on. I'm coming to you in a second. I want to talk to Terry first. Terry is in Salt Lake, Utah - Salt Lake City, Utah. Terry, welcome to the show.

TERRY: Yeah, hi. I'm old and retired now. But something I know, that crime goes up and down. My wife worked in a big city on the East Coast, and it goes up and it goes down. It's the type of crime, senseless violence. You go on a call and two guys are beating the heck out of each other, and you hear from both sides and you just go, this is - these kind of people wouldn't totally fight over this kind of thing. And on the other hand, certain kinds of crime go down. People you expect - street types, drug addicts and so forth - just seem to be a little bit less active when it gets really hot. So it goes up and it goes down. It depends on the kind of crime you're talking about.

COX: OK. Thank you very much for that, Terry. Steve, now I'm coming to you in Visalia, California. Steve, welcome to TALK OF THE NATION.

STEVE: Well, thank you for having me. I'm actually a deputy public defender here in Tulare County. Visalia is the county seat. I have to say I'm quite skeptical for lots of different reasons. And it's obvious that there seems to be some correlation here, but I'm not sure you can ever get to causation. And let me just mention a couple of things. I'm in one of those places where we're well above 85 degrees for much of the year. And sure, there's more crime here when it's hot than there is when it's cold, but there's more everything here when it's hot than there is when it's cold.

And there are other things that I think are more important to these variables than just heat. And by that I mean that I think what influences crime primarily is mental illness and drug abuse. Both of those things cause the criminal perpetrators to be irrational. And if you're talking about an irrational actor, you would have to think that their irrational response to heat would be just as irrational as it would be to everything else.

And so, while I think it may be somewhat true that we get hot and sweaty and are more likely to punch someone in the nose as a result of our being irritated, I don't think we'll get much causative value out of making conclusions based on such a small variable.

COX: That's a very interesting point, Steve. Thank you very much for calling. As a researcher, Brandon, do you find that the studies in this area, are there many and are they all pretty much along the same line? Or is this an area that is not considered particularly scholarly worthy?

KEIM: Well, it's certainly scholarship worthy, and it's something that people have been interested in for hundreds of years. And, certainly, the standards in the early studies were very, very loose. And you know, there's much talk about, you know, all those hot-blooded Southerners and their wild cultures of violence. But that said, it's not like it receives tons of attention. This isn't something that, you know, there's thousands of researchers working on. And, you know, I believe what the caller just said about not drawing conclusions is absolutely correct.

There are no hard and fast conclusions to be drawn right now and, you know, to go from correlation to causation is impossible at this time. But I think there are a lot of interesting questions that are raised and lots of interesting speculations about the, you know, the nature of human behavior and its intersection with, you know, weather itself. Not a lot of fun to think about, certainly.

COX: All right. Let's take a couple of more calls. This one is from, I believe it is pronounced Stenio(ph) in Tallahassee.


COX: Hi. Is it - are you Stenio?

STENIO: Yes. You got it right.

COX: OK. Welcome.

STENIO: Yes. I do see that there's a relationship between heat and violence, sometimes maybe not violence but also bad temper. I have my experiences from when I served in the United States Navy. And people that works in the boiler rooms, people that works in the boiler rooms are working in sometimes like 10 to 12-hour shift in temperatures like 85 degrees and over. And in those environments, you always know that there's an increase in the bad temper, people with anger, and there's a lot of fighting. It's because of the heat. The heat makes you be mad and angry.

COX: Thank you, Stenio, for that. Although some might suggest, Brandon, that working 12-hour shifts can make you mad and angry as well, no matter what the temperature is. Let's go to Jacob in Sioux City, Iowa. Jacob, welcome.

KEIM: There are confounding variables.

COX: Yes, there are. Jacob, welcome to TALK OF THE NATION.

JACOB: Hi. Thanks for taking my call. I am a sergeant with the Sioux City Police Department here in western Iowa. During the summer months, especially around June and July, we see a large increase in the amount of simple assaults. And personally, I believe a lot of this is possibly related to - I mean, there's an increase in temperature. But mostly I think it's the social interaction between people. There are so many more people that are out and about, you know, a lot of people drinking more alcohol and whatnot.

And, you know, just getting people together in those situations, you know, it, you know, it is hotter, people have a little bit shorter, you know, they - it's easier for people to get a little upset when they themselves are uncomfortable. And - but I definitely do see a larger increase in these kind of acts.

COX: OK. Jacob, thank you very much for the call. So there is a connection, just what - how much of a correlation there is isn't clear. But we do have on the line now from Detroit. This is Paul. And Paul is in law enforcement - and as I understand it, Paul, your department has just been talking about this?

PAUL: Yeah. Actually, that's correct. We had a seminar that we went to about two weeks ago when the heat wave hit here about what to expect, how to change our tactics on patrol. And basically what we were told to expect we found. Your previous (technical difficulties) mention of simple assault. That's what we're finding as well as, interestingly enough, an increase in domestic violence. We found ourselves responding to calls of domestic violence, I'd say probably about a third more than usual.

So I mean, again (unintelligible) previous caller, I'm not sure if you can equate that to causation, but it is definitely interesting to deal with a new variety of crime. Well, not a new variety but a certain variety in a much more heightened sense.

COX: Paul, hold on. I want you to hang on. I have a question for you. I just want to let people know that we are talking about heat and crime. And you're listening to TALK OF THE NATION from NPR News. So Paul, here's the question for you. As a Detroit cop...

PAUL: Yes, sir.

COX: you find that police officers are affected by the heat in terms of how -their temperament when they're dealing with people who are committing crime or suspected of it?

PAUL: Absolutely. And, you know, let's just - it's the same thing. I mean, if you have people on the street that's going to be affected by the heat and you raise their aggression, it may lower their ability to control their own reactions, I mean police officers are people too. You know, we're going to find that if we're especially on foot patrol or bike patrol, that the heat gets to us and, you know, I have definitely experienced where I would see people who are usually very calm under pressure (unintelligible) you know, the 110 heat index for hours at a time, it can definitely decrease your ability to maintain control.

COX: Paul, thank you very much for that. Brandon, here's an email from a listener I'd like you to respond to, if you can. It comes from Hannah in Rochester, New York. She says: My question is, do we know if the heat-crime correlation has changed over time? I wonder if, in the days before air-conditioning, heat did not have the same effect. Part of what makes heat so unbearable may be the feeling that it is unavoidable or that it is avoidable. Is there historical data on this?

KEIM: Hmm. I'm not aware of any two data sets that have been compared across that gap. Certainly there's data before and after that of air-conditioning, but I don't know if it's the type of data that you could make a, you know, apples-to-apples comparison on. But I would just throw out there also an alternative explanation, which would be that in a world without air-conditioning, when we're actually accustomed to heat, maybe it would bother us less than, you know, when we're in our homes and it's 65 degrees and everything is lovely. And then you go outside and it's 95 degrees. And that transition is so abrupt and percussive that I (technical difficulties) think it could actually, you know, get more on our nerves.

COX: I appreciate that answer. I - we've been getting a number of calls and a number of emails about this. And they are, in the main, anecdotal. Peopling saying, well, in my situation it's this, or in my situation it's that. And we're not able to draw conclusively, it seems, of a causation between heat and crime. Certainly people get more angry. Certainly their tolerance level goes down, and their activity level perhaps is affected by the heat. But it's an interesting area to research. Are you intending to - my last quick question for you, are you intending to continue your research in this area?

KEIM: I certainly will. And one little research note I'd like to end with is that there was an interesting study in the late '70s, where researchers found that you could calm angry people down a little bit by giving them a cool drink, which makes sense.

COX: That's interesting. I've heard that before in my own household when I was a kid. Thank you very much. Brandon Keim is a science reporter for Wired magazine, where his article "The Hazy Science of Hot Weather and Violence" ran on July 22. There's a link to that on our website at Just click on TALK OF THE NATION. Thank you again, Brandon.

KEIM: Thank you. Have a good one.

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