Perry and Simpson examined the relationship among several environmental variables, including monthly and seasonal cycles, temperature and precipitation, and the monthly rates of murder, rape, and aggravated assault in Raleigh, N.C. They suggest that the positive relationship between precipitation and assault may be due to precipitation's reducing the levels of out-of-home activities and increasing the levels of frustration due to disruption of planned activities. However, they do not distinguish between acquaintance crimes and stranger crimes. They also suggest that warmer weather and increases in daylight increases activity, exposure to risk and opportunity for criminal activity. However, they do not discuss possible mediating factors such as alcohol consumption. Perry and Simpson also fail to mention major biological theories about the effect of weather on behavior. Although their study is one of the better ones on weather and crime, they have not used any of the time-series modeling techniques developed to deal with these types of data. They have also ignored many weather variables that could influence violent crime. Nevertheless, their research makes an important contribution to a new and vital area and could lead to improved criminality prediction, which would aid both the public and criminal justice agencies. 27 references (Author abstract modified)