The impression that violent crime headlines pile up during the worst summer heat waves isn't baseless. Multiple studies examining the correlation between temperature and crime rates have confirmed exactly this trend. Here's what the numbers show and how it's explained.
A study published in 2011 found that violent crime and homicide rise by about 32 incidents per 100,000 people for every 1°C increase in temperature. The World Economic Forum's report on heat waves and mental health similarly found that violent crime rises 3-5% for just a 1-2°C increase in ambient temperature, and projected that climate change could raise global crime rates by up to 5% by 2090. Studies within Korea have likewise found that reports of violence and sexual assault tend to rise as temperature and humidity increase.
Research published in journals like Scientific Reports has found that serotonin, a neurotransmitter involved in suppressing aggressive tendencies, is vulnerable to high temperatures. Extreme heat impairs the body's temperature regulation, increasing discomfort and reducing cognitive function — experts point to these physiological changes as linked to increased aggression.
Beyond heat's direct physiological effect on the body, weather also changes people's behavior patterns. In hot weather, people spend more time outdoors and in public, increasing social contact — which naturally increases the opportunity for conflict or confrontation. Researchers have found that temperature and season have a far larger effect on violent crime than on property crime like theft, which is interpreted as physiological and opportunity-based factors working together.
Extreme heat is directly tied not just to aggression but to heat-illness risk too. Checking days with a high feels-like temperature in sanCheck ahead of time can help you reduce stress in hot conditions and adjust when you head outdoors.