Hot weather is related to urban unrest — as it was in 1967 — and climate change is bad news for that

Some say it was so hot you could see the heat shimmering off the pavement, that as it rose from the ground, it put a distorted haze in the air. Others remember fire hydrants cracked open and children vying for a stream of cool water. And then there were those who crouched under the awnings of downtown buildings, desperate for a sliver of shade. This was the summer of 1967 in America.

“Ah, it was hot. July 1967 was hot. It was hotter than hell!” recalled Richard Rybinski, who worked for the Detroit housing commission at the time.

During this remarkably hot stretch, temperatures raced into the upper 80s and 90s across much of the United States. The grueling heat wave stoked already fragile emotions and in the inner cities — places like Detroit, Chicago, and Newark — tempers flared under the blazing sun. By the time fall had arrived, and the temps had subsided, 159 riots had erupted across the nation, leaving many dead and wounded, and thousands behind bars.

“The arrival of the summer increasingly became associated with rising racial tension and it seemed that, whenever the mercury headed up through the 80s and 90s, anger would begin to reach a boiling point,” writes author Malcolm McLaughlin in his book The Long, Hot Summer of 1967: Urban Rebellion in America.

Since the riots, a growing body of evidence suggests an association between summer heat and violence, that elevated temperatures exacerbate anger and trigger aggressive actions. In fact, even a moderate change in climate toward warmer temperatures can cause the frequency of interpersonal violence to rise by 4 percent and the frequency of intergroup conflict to rise 14 percent.

“There is good evidence that heat can increase the likelihood of violent action, including riots,” says Craig Anderson, a professor of psychology and the director of the Center for the Study of Violence at Iowa State University. “In other words, it is a risk factor. However, virtually all violent actions require the presence of multiple risk factors, with some type of provocation being the most important.”

In Detroit, which witnessed the most violence and bloodshed, there were plenty of social, economic, and political risk factors that had culminated over decades: segregated housing and schools, rising black unemployment, and a nearly all-white police force prone to heavy-handed arrest practices. The weather may well have been the final provocation.

And, the magnitude of personal suffering depended directly on a person’s address, the amount of money they had in their pockets, and, by extension, the color of his skin. Those in the poorest black neighborhoods were trapped without a reprieve from the heat that blanketed the inner city.

“People didn’t have air conditioning, buildings didn’t have air conditioning, it was really hot. I mean it was just muggy, crappy hot. I think you had some people that were just angry about everything in the world,” former Detroit resident Sandra Smith said in an interview.

On July 23, 1967, as temperatures soared in Detroit, vice squad police officers raided a blind pig, an illegal after-hours bar, on the corner of 12th Street and Clairmount Avenue. Despite the late hour, people were heavily congregated in the center of the city’s oldest and poorest black neighborhood. Many had wandered outside to escape the heat. Others were at the unlicensed bar to celebrate the return of two black servicemen from Vietnam. As the police arrested some of the bar’s patrons, the crowd around the establishment grew larger and the situation quickly escalated.

“That day, when the riots broke out, it was so damn hot. I remember it like yesterday,” says Doris Vansen, who lived in the University District and was 11 at the time. She had planned on taking a quick bike ride that evening to cool off, once she had finished her chores. But as she knelt on the warm ground, pulling weeds from her parents’ front lawn, her father leaned out the screen door. “My dad told me I couldn’t go, because there was a sniper on top of the Montgomery Ward over on Livernois Avenue. I didn’t know what the hell a sniper was. I was too young. I didn’t know.”

Some families slept on their porches during the heat wave. Virgil Taylor was awoken by the sound of footsteps the morning of the riots. Through the slats of his porch railing, he watched as a crowd of people dashed by his house, just one block from the raided bar. Their arms and pockets were full of stolen goods. “I knew some of the people looting and they weren’t angry. They were just opportunists taking advantage of the situation.” Soon after, he says the 101st Airborne was called in and they turned a local school campus into a military base.

Gail Gargaro Storer had just turned 12 in the summer of 1967. Her family, the developers of the Avenue of Fashion, belonged to the Detroit Golf Club. To this day, she believes the heat played a vital role in the uprising. “It was so hot that summer, I remember black children were sneaking onto the property. They climbed the fence and tried to use the club pool. Employees just sent them away, telling them it was a private, member-only club. That had never happened before.”

The day the riots started, she and her siblings were down at the golf club swimming. “The club shut down when the news broke. I remember the ride home was terrifying. It took us over two hours to get back to our house, when it was normally a half-hour drive.”

Over a span of five days, in which the Detroit police and fire departments, Michigan State Police, National Guard, and U.S. Army were involved, forty-three people lost their lives, hundreds were injured, and thousands were arrested in what became the largest civil disturbance in 20th-century America. Seasonal urban unrest, however, was not a new occurrence.

A similar wave of violence rippled through the United States in the summer of 1943. The chain of events and mediating factors echoed those of 1967. Institutional racism. Entrenched segregation. Poverty and white police brutality. Tensions were ripe and the heat of that summer also fueled irritation into action. On June 29, 1943, a riot broke out at Belle Isle Park in the heart of Detroit. Six thousand federal troops were called in to suppress the situation, which claimed thirty-four lives and caused more than two million dollars in property damage. The Detroit riot was one of several that summer, following one in Beaumont, Texas and preceding another in Harlem.

More recently, in 2016, the United States experienced another heat wave, with temperatures soaring beyond 100 degrees in many cities. This was the same summer that protests erupted in response to the officer-involved shootings of Alton Sterling and Philando Castile. While the situations were contained before more lives were lost and property heavily damaged, the circumstances mirrored those of previous summers. Many held their breath, waiting, and wondering, “Will this be a repeat of 1967?”

Although researchers believe high temps can make people irritable, impair judgment, and inhibit self-control, there is no clinical or laboratory evidence that links the two together. “I suppose ethical issues would mean nobody could put people in a position where they were expected to be violent, so I don’t expect to see such medical evidence,” says John Simister, senior lecturer at Manchester Metropolitan University, who has studied the link between violence and hot weather. But statistical data shows there is indeed a relationship: urban unrest in cities occurs with greater frequency and more violence during relatively warmer months.

And more summertime riots are expected as climate change pushes the mercury even higher. “It’s clear that global warming is happening, and it’s clear to me, and to many other researchers, that more extremes of heat will lead to more violence, including riots,” Simister says.

As a nation, as individual communities, and even on a micro level, we’re not at all prepared. Not for the heat, not for increased urban unrest, and certainly, even though we’ve had fifty years to make progress, not for the continued vicious cycle of white privilege and economic inequality that often leads to violence.

It’s only a matter of time, and another heat wave, before we face the consequences again.