A whole house fan is most effective at cooling homes in areas that have hot summer days and cool nights.  They work best in areas where humidity levels are lower.  Like in Region 1 above, a whole house fan can eliminate A/C usage nearly 90% of the time. 

In Region 6 - Your whole house fan could be used to as a air conditioning assist - meaning you would use your fan to remove a large percentage of the ambient heat in your home and attic.  After exhausting your home (and turning your fan off), your air conditioner will run much more efficiently, cooling your home quicker.

In Alaska - Using a whole house fan - eliminates the need for air conditioning.