Why mass shootings and violence increase in the summer

Former New York City police officer Jillian Snider, now a lecturer at the John Jay College of Criminal Justice, said she saw this firsthand in neighborhoods where a lack of air conditioning pushed people out onto their stoops or into parks on sweltering days.

“It makes people a little angry because there’s nowhere to cool down and tensions rise,” she said. “You have no escape from that, you’re just more upset.”