Some other things to consider:

1. The cooler it is outside, the farther the temp will drop overnight.
Even if it doesn't drop much, at least you get fresh air in. In the
fall, I was able to pull in warmer air during the day and raise the
temp in the house by a few degrees.

2. Since you have to leave windows and doors open, consider the
security issue.

3. You'll be pulling in dust from outside.