Quick history lesson...
Boston created a night watch in 1636, New York in 1658 and Philadelphia in 1700. The night watch was not a particularly effective crime control device. Philadelphia created the first day watch in 1833 and New York instituted a day watch in 1844 as a supplement to its new municipal police force. It was not until the 1830s that the idea of a centralized municipal police department first emerged in the United States. In 1838, the city of Boston established the first American police force, followed by New York City in 1845, Albany, NY and Chicago in 1851, New Orleans and Cincinnati in 1853, Philadelphia in 1855, and Newark, NJ and Baltimore in 1857. By the 1880s all major U.S. cities had municipal police forces in place.
That is right, some form of police work or "night watch" or "day watch" (which it is still called in many areas) has been around since over a hundred years before the revolutionary war. Guess what we have known since those days? When it gets warm outside, there is a spike in crime, in general disorderliness and general drunkenness (or the use of substance for recreation). None of this is new, none of this is ground breaking, none of this is something which cannot be taken into account.
This year we have had a longer than normal winter/cold season. This means that we have had less violent crime due to the weather, but do not worry, Summer is Coming. When we hit those 90+ degree days you will see a huge spike in crime, I have already seen it on those random hot days, the brass think its an anomaly. Of course they would believe that, they are the anomalies.