Does Sacramento see more violent crime on hot days? See what data shows when temps spike
Violent crime rises on hot days, according to decades of research, and this trend hold true in Sacramento.
During the most recent heat wave from Sept. 1 through Sept. 9, police reported about 5.3 aggravated assaults and 4.2 robberies each day — well above the averages on most days.
Robbery is stealing something from a person by force or the threat of force. Aggravated assault is attacking someone with the intent to inflict severe injury. It usually involves a weapon or some other instrument likely to produce death or great harm.
The most common types of violent crime tend to increase on very hot days in Sacramento, while the most common types of property crime tend to decrease, according to a Bee analysis of recent data from the Sacramento Police Department and National Weather Service.
From January 2020 through September 9, there were 72 days in Sacramento where the temperature reached at least 100 degrees.
Sacramento Police reported an average of 4.1 aggravated assaults on those hot days, about 23% higher than the average reported on cooler days. Similarly, police reported an average of about 3.1 robberies on hot days, roughly 13% higher than the average reported on cooler days.
In addition, police reported, on average, more robberies and aggravated assaults during the last three years on summer days when temperatures reached 100 degrees than on milder summer days.
On the other hand, Sacramento Police reported an average of 11.9 burglaries on hot days, about 20% lower than the average reported on cooler days. They reported an average of about 17.9 larcenies on hot days, roughly 6% lower than the average reported on cooler days.
A burglary is defined as the unlawful entry of a structure with the intention of committing a crime. Larceny involves taking the property of another person without their permission or with the right to do so.
Researchers have found similar trends across the country. For instance, a 2017 study by Drexel University researchers found that violent crime was 9% higher in Philadelphia when the temperature was 98 degrees than when it was 57 degrees.
Researchers differ on why the phenomenon occurs. Several have posited that people are more likely to go outside when it is warmer, and violent crime tends to take place outdoors.
But that explanation may not explain why violent crime is higher when it is very hot - so hot that most people may stay indoors with air conditioning and fans.
Iowa State researcher Craig Anderson argues that the heat itself is a driving factor because it makes people more irritable and more likely to act out. One of his studies on the topic states that “results show that global warming trends may well increase violent-crime rates.”
Wired reporter Brandon Keim summarizes Anderson’s argument this way: “In hot weather, the body exhibits changes -- increased heart rate, blood circulation and sweating, and metabolic changes -- associated with sympathetic nervous system activity, which in turn is linked to fight-or-flight responses. Hot weather also increases testosterone production, tilting that equation towards fight.”
This story was originally published September 27, 2022 at 5:00 AM.