A couple weeks before this posting, I read this extremely grim article from the New York Times (I know, surprising, right?) about a study concerning blackouts during heatwaves and their effect on death and illness. The conclusion of this study is fairly easy to see: a blackout during a heatwave
Also used the blankets on the south-facing windows last summer and they did help.
If someone else wants to try it out, make sure to attach em on the outside, not the inside of your windows. Attaching them on the inside might cause the glass to shatter from the heat.