It’s common for law enforcement agencies to experience an uptick in crime during the summer months.

Some city departments deploy extra officers when the weather warms up and crime rates rise. But in other, typically warmer areas, summer isn’t all that different than other seasons.

To gauge typical crime patterns, Governing reviewed monthly data that 384 larger law enforcement agencies reported to the FBI between 2010 and 2012. On average, monthly crime for seven major offense types increased nearly 10 percent between June and August from the rest of the year. The majority of agencies reviewed serve warmer jurisdictions that typically don’t experience large drop offs in crime during the winter months. For other cities, though, stemming violence in the summertime is a far more difficult task.

While it’s too early to say how most cities fared this year, many police agencies and local governments initiated efforts aimed at limiting summer crime. The New York City Police Department, for example, deployed additional cops and reassigned those at desks to troubled areas for its “Summer All Out” initiative. In Minneapolis, police similarly stepped up foot patrols following a sharp increase in shootings this summer.

Areas where crime surges the most in the summer tend to be northern cities in states like Minnesota and New York. In all, 42 police agencies reviewed recorded average increases of greater than 20 percent compared to times of the year.

“It’s almost a cliché in the northeast that things get busier in the summer for police,” said Michael Maxfield, a professor at John Jay College of Criminal Justice in New York. “They expect it.”

In Erie, Pa., totals for the seven major crime types rose by an average of 35 percent during the summer months -- one of the highest increases nationally. The city’s harsh winters likely help push down crime totals, and police there also see more activity from visitors during the summer months.

A few of the law enforcement agencies that registered the steepest fluctuations in crime serve summer tourist destinations. Take Virginia Beach, Va., for example, where crime increased an average of nearly 23 percent. A few million people visit the city’s oceanfront each year, and agency statistics indicate about 30 percent of those arrested annually are from outside the Hampton Roads metro area.

Some smaller resort towns hire seasonal police during the summer. Depending on their training, these uniformed officers may lack full police powers and could perform traffic enforcement and related duties.

The following table shows changes in average monthly offenses for law enforcement agencies with published monthly data serving at least 100,000 residents.

Summer Crime on Average

NOTE: Offense totals include murder/manslaughter, rape, robbery, assault, burglary, larceny and motor vehicle theft. Violent crime includes murder/manslaughter, rape and robbery.

SOURCE: Governing analysis of 2010-2012 FBI UCR Data. See "Notes on Data" below

A number of theories offer varying explanations for higher levels of crime in the summertime.

Jerome McKean, an associate professor at Ball State University, said it’s mostly that there are just more opportunities for crime to occur. “There’s a large pool of potential offenders and victims who are more vulnerable that time of year,” he said.

Teenagers, in particular, lack activities to structure their time while out of school. It’s this group that’s been a particular focus for several cities. The city of Los Angeles partnered with a foundation for its “Summer Night Lights” program, offering evening activities at area rec centers and parks that target youths at risk for gang involvement and related violence.

Tourists run a greater risk of having bags or valuables stolen while they’re traveling, McKean said. And when they’re out of town on summer vacation, their houses are prone to break-ins.

Some have even blamed hotter temperatures for more crime, arguing such weather causes more aggressive behavior. Both Maxfield and McKean, though, expressed skepticism of that theory.

While warmer temperatures may not necessarily cause crime, multiple studies find it does correlate strongly with higher crime levels. A recent study published in the Journal of Environmental Economics and Management takes it a step further, using a model to estimate additional crime caused by climate change. Evidence also suggests crime declines once temperatures reach a point where it’s too hot for people to want to be outside. Two Florida State University researchers found that assault rates began to drop once temperatures reached about 80 degrees Fahrenheit over a two-year period in Minneapolis.

Agencies serving jurisdictions with warmer temperatures outside the summer months were shown to have much smaller seasonal fluctuations in crime in the Governing analysis. Agencies in warmer climates experienced an average monthly increase of about 6 percent during the three summer months, while crime rose nearly 18 percent in colder climates.

SOURCE: Governing analysis of 2010-2012 FBI UCR Data

Some police departments actually experience slightly less crime in the summer. The Scottsdale (Ariz.) Police Department reported total murders, rapes and robberies that were an average of 7 percent lower. That’s not surprising considering peak season for tourism there falls outside of summer, and daily highs regularly exceed 100 degrees from June through August.

Many agencies reviewed not experiencing spikes in summer crime serve jurisdictions in Arizona and California.

Seasonal swings in crime occur also vary for different types of crimes. Cities often experience far more property crimes during the summer, likely attributable -- at least in part -- to the fact that the primary perpetrators aren’t in school. Pittsburgh police receive more reports of nuisance-type crimes, such as car break-ins and graffiti, during the summer months, according to Sonya Toler, a city police spokeswoman.

Murder counts climb in the summer months as well. Police agencies reviewed saw monthly murders increase an average of 15 percent from June through August, with larger variations occurring in places like Cleveland and Rochester, N.Y.

To keep summer crime to a minimum, some agencies turn to increased staffing and extra patrols. The New York City Police Department reported a 25 percent drop in shootings in 10 targeted precincts following the implementation of its initiative in July.

Seattle launched a broader “Summer of Safety Initiative,” coordinating efforts across multiple departments. Part of the city’s efforts encouraged residents to report nuisance issues, such as abandoned vehicle and graffiti, along with public safety concerns. Hours at libraries and community centers were extended. Like other cities, Seattle also runs a summer jobs program providing opportunities for young adults to work for the city or participating local companies.

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Notes on the Data

  • Seven types of crime were reviewed for this analysis: murder/manslaughter, rape, robbery, assault (all types), burglary, larceny and motor vehicle theft. Data was compiled from the FBI's Uniform Crime Reporting (UCR) program for 2010-2012.
  • Law enforcement agencies that report monthly UCR data and serve at least 100,000 residents were included in the analysis. Agencies that either do not participate in the UCR program or do not report monthly offense data were not included. The New York City Police Department, for example, reports crime data on a quarterly basis.
  • The 384 agencies reporting data are not necessarily representative of the nation as a whole. Most serve jurisdictions in warmer climates, so the 10 percent average difference in summer crime would be higher if additional larger jurisdictions elsewhere reported monthly data.
  • Some smaller agencies reviewed reported relatively few crimes.
  • Monthly figures were not adjusted to reflect the number of days in each month. 
  • Agencies were categorized into cold, mild or warm climate groups based on their state’s average mean temperatures for non-summer months.