Two researchers from Drexel University’s Dornsife School of Public Health found that rates of violent crime are higher on days with higher temperatures. Their research was recently published in the Journal of Urban Health.
Leah Schinasi, assistant research professor, and Ghassan Hamra, assistant professor, conducted a time series analysis on 10 years of data from 2006 to 2015 in Philadelphia. They found that there was a strong association between violent crime, disorderly conduct and the temperature.
Schinasi and Hamra found that this was the case for all seasons, not just summer.
“Overall, these analyses suggest that disorderly conduct and violent crimes are highest when temperatures are comfortable, especially during cold months,” an excerpt from their abstract reads.
They looked at crime data from the Philadelphia Police Department and weather data from the National Centers for Environmental Information. From this information, they made a distribution of mean daily heat index. Schinasi and Hamra found that when the mean daily heat index was in the 99th percentile, the rate of violent crimes was nine percent higher.
Between May and September, crime rates were overall the highest. In these warmer months of the year, crime rates increased seven percent when the temperature reached 98 degrees. In the colder months between October and April, the effect of weather on crime rates was more drastic. In these months, crime rates increased 16 percent when the temperature reached 70 degrees.
Schinasi and Hamra also took into account daily deviations in the temperature from the seasonal norms to see if unusually warm days had an effect on crime. They found that the rate of disorderly conduct was seven percent higher on days that were at least 55 degrees warmer than average during cooler months.
“When temperatures are extremely cold or hot, people stay indoors. But as temperatures become more comfortable, more people are outdoors, which presents greater opportunity for crime,” Schinasi told DrexelNow.
Comfortable weather tends to lead to more people spending time outside. However, crime rates remained relatively steady in hotter months when there was a cooler than average day.
“I could speculate about the reasons that cooler, more comfortable summer temperatures are not associated with higher rates of crime, but I am honestly not sure,” Schinasi told DrexelNow.
Schinasi believes that more neighborhood-specific research would be helpful in identifying additional crime variables.
“Additional analyses that tease apart these effects will help us better understand these findings and seasonal trends,” Schinasi told DrexelNow.
These findings are of particular significance as the global temperatures are rising.
“It is important to recognize the implications of these climate change effects for public health, including changes in crime rates. Although these results back up police officers’ anecdotal reports about the relationship between temperature and crime, it’s nice to have data to confirm these reports. Our results might help inform local law enforcement about ways to allocate resources during different seasons with consideration of the local climate,” Schinasi told DrexelNow.