Hot Temperature and Lack of Seasonal Variation Contributes to Violence and Aggression

Do you ever wonder why violent crime is more common in regions with hot climates? A new theory from researchers from Vrije Universiteit Amsterdam claims that hot temperatures and little seasonal variation contribute to more violence and aggression.

According to the CLASH (Climate, Aggression, and Self-Control in Humans) model developed by researchers, people living in countries with hot climates and little variation in temperature across the seasons tend to behave with less self-control and put less importance on the future. People in these regions live a faster lifestyle and spend less time planning for the future. As a result, they can be more aggressive and violent.


Pail Van Lange, a professor of Psychology at Vrije Universiteit Amsterdam, believes the CLASH model can help explain the effect of climate on rates of violence across the globe.

“Climate shapes how people live, it affects the culture in ways that we don’t think about in our daily lives.”

Two previous studies have found the relationship between hot climate to violence and aggression but fail to give a satisfactory explanation, according to Brad Bushman, a Psychology professor at The Ohio State University and VU Amsterdam.

Based on the General Aggression Model, aggression in hot climates is attributed to discomfort and irritation. This, according to Bushman, can’t account for more extreme acts of violence like murder.

Meanwhile, the Routine Activity Theory which says that warm weather causes people to stay outdoors more often and creates more opportunities for conflict doesn’t explain why violence increases as the temperatures go higher.

In the new theory, researchers believe that less variation in temperature along with heat make people have less of a need to plan ahead for weather differences. This makes them less concerned about the future and have less need for self-control.

What is the difference between violence and aggression?

We often use the terms aggression and violence interchangeably, but these words are not the same. According to, violence refers to the use of physical force with the goal to injure another person or damage a property. Meanwhile, aggression is defined as violent feelings or behavior. An aggressive person does not necessarily act out with violence.