Does Heat Trigger Violent Crime?..."Number of Gunshots Increases as Weather Gets Hotter"

"On Warm Days, Often Occurring on Weekends or Holidays"
Research Also Shows Violence Increases with Rising Temperatures

Recently, indiscriminate stabbing incidents have occurred one after another, becoming a social problem. Amid this, a study from the United States has revealed that hot weather may influence the occurrence of violent crimes.

On the 13th, a joint research team from the Columbia University Mailman School of Public Health and Harvard T.H. Chan School of Public Health announced the results of a study examining the correlation between gun-related incidents and weather in Chicago, USA. According to the study, as the average daily temperature rises, the number of shootings per day increases.

The research team stated, "In recent years, shootings in Chicago have occurred more frequently on warm days, especially on weekends or holidays." This aligns with other research findings that link crime to higher temperatures.

[Image source=AP Yonhap News]

In fact, in 2014, when the weather became sunny in Chicago, there were as many as 36 shootings within 36 hours. During the sunny weekend from April 11 to 14, 2014, at least 37 shootings occurred, resulting in 4 deaths and 33 injuries.

Notably, from 3:30 PM on Friday the 11th to 3 AM on Sunday the 13th?a span of 36 hours?a total of 36 shootings were confirmed. At that time, the highest daytime temperature in the Chicago area on the 12th was recorded at 27 degrees Celsius, the highest of that year.

According to the researchers' data, the average daily temperature in Chicago from 2012 to 2016 was 15.3 degrees Celsius, during which a total of 14,633 shootings occurred. Arithmetically, this equates to an average of one victim every three hours. When the temperature rose 10 degrees above average, the overall shooting rate increased proportionally by 33.8%. On weekdays, shootings increased by 34% with a 10-degree temperature rise above average, and on weekends or holidays, shootings increased by 42%.

Looking at the data by month, the average number of shootings was lowest in February, while August saw the highest average with 8 shootings per day. Especially on weekends (more than 10 shootings) and holidays (up to 9 shootings) in August, the numbers were higher.

The research team pointed out, "The timing when shootings are likely to occur can be as important as the location." The study was published in the international journal Injury Epidemiology in July 2020.

A joint research team from the French National Institute of Health and Medical Research and the Institute of Psychiatry, Psychology & Neuroscience at King's College London also released findings that seasons influenced mass shooting incidents in the United States from 2013 to 2015. This report was published in May 2016 in the American Journal of Public Health.

At that time, the research team obtained public data on all mass shootings in the U.S. from 2013 to 2015, defining mass shootings as incidents where four or more people were shot. The results showed a clear increase in the number of deaths and injuries from shootings during the summer, a pattern that repeated annually over the three years.

Shooting incidents began to increase from May, peaked in August, and then declined from September to October. The research team described this as a "significant seasonal effect," noting that seasons influence moods such as hostility, anger, irritation, and anxiety.

Similar statistics on the seasonal impact on violent crimes have been studied domestically as well. According to the 2010 Crime Analysis White Paper released by the Supreme Prosecutors' Office in 2011, a notable correlation between weather and crime was observed.

In 2009, out of 1,390 murders, 652 cases (46.9%) occurred on clear days, showing the highest frequency. Violent incidents also concentrated on clear days, with 24,260 out of 59,016 cases (41%). Other violent crimes such as rape (39%), theft (36%), and robbery (38%) similarly showed a high concentration on clear weather days during the same period.

There is also research indicating that rising global temperatures significantly increase violence and aggression. According to a 2021 study by the U.S. National Bureau of Economic Research (NBER), soaring temperatures are known to worsen mood and condition, thereby increasing violent tendencies. The study found that when the heat index exceeds a certain threshold, violent interactions increase by 20%, and the likelihood of violence rises by 18%.