The old expression, "It's not the heat, it's the humidity," definitely applies for August 2002. Although dry bulb temperatures and sensible cooling ventilation load indexes (VLIc's) were higher than normal for most of the country, it was the long duration of simultaneous high humidity levels that really had an impact on ventilation costs.
In fact, Boston, Chicago, Cleveland, Memphis, Detroit, and Washington, DC all saw latent VLIc's that were at least 40% higher than normal. Boston topped off the list at +56%. What was the impact? In Boston, with an assumed blended electric rate of $0.10/kWh and 0.75 kW/ton cooling efficiency, the total ventilation cooling for August 2002 was 2.15 (Figure 1) x 0.75 x $0.10 = $0.161/cfm. Compare that to the norm for August of 1.58 (Figure 1) x 0.75 x $0.10 = $0.119/cfm.