You might look at the Uniform Crime Report for your state, or the overall report from the DOJ/FBI. The 2001 Virginia report has some interesting charts. Murder is fairly stable, except for a peak in December and dip in February. (February seems to have the lowest crime of any month, maybe because it's cold and short.) Violent crimes like rape and assault peak in the late summer and drop off drastically during the winter and spring. On the other hand, crimes like burglary and motor vehicle theft seem more common in the late fall and early winter.
The peak time for violent crime in VA is between midnight and 1 AM, especially on Saturday (i.e., late Friday night).
I found it interesting that drug arrests peaked in February and March. Could this be because these are the lightest months for other types of crime?