In Washington DC, killings are down for the year after a summer that has seen 44 percent less murders than last summer. The Washington Examiner had this report today:

As temperatures climbed relentlessly this summer, homicides in the District fell just as dramatically, something a leading expert says may not be a coincidence.

Since Memorial Day weekend two months ago, the number of killings in D.C. has dropped by 44 percent compared to the previous year. Before the holiday, which traditionally kicks off the summer season, homicides in D.C. were up 16 percent. The pace of killings in the city have slowed so that homicides for the year are down 12 percent and violent crime is down 7 percent, according to police records.

Criminologists, the story notes, "have long noted that crime can rise in the summer months. People become more aggressive and lash out. Rapes, riots and 9-1-1 calls go up. Part of that is that teenaged males are out of school and unsupervised, the days are longer, and outdoor activities increase. But searing heat may drive people indoors, and even dull the ardor to keep cycles of revenge killings going."

DC and Prince George's County went homicide-free during the record-breaking heat, and so did Baltimore, with six days going by before a spate of killings this week. But for the summer, Baltimore isn't enjoying the same lull in violence. While DC has seen a 44 percent summer drop, there have been the same number of killings in Baltimore since Memorial Day, 40, as there were during the same period last year. DC has seen just 18 summer killings, down from 32 at the same point last year.