In NYC, Murders Mirror Mercury

Summer heat brings people onto the streets—and the murder rate up, the New York Times reports. In the city, September is historically the worst month for homicide, according to an analysis of police data. August is a close second. And the deadliest time? 10pm on a September Saturday. “Homicides vary with social acting,” a criminology professor said. “It evolves from interactions.”

The analysis shows that murder is more likely when people socialize and use alcohol and drugs—weekend-evening pursuits. And the warm summer air encourages partying and its deadly corollary. More than a third of recent homicides in New York happened Saturday or Sunday. And the darkness is getting deadlier: In 1981, 29% of murders occurred between midnight and 8am. In 2008, it was 39%. (More New York City stories.)