People always ask what we still do from our no impact year, and one thing is that we got rid of both our air conditioners. There are seven or eight nights in the summer where it's really hot in New York City, but we keep a tub of cold water ready to hop into and that gets us back to sleep.
Today, though, was the first of New York's 85 degree days in 2009 (in April!). What we do is close all our windows during the day and keep all our shades closed so the sun and hot air can't get in. The result? We needed long sleeves in the apartment.
If you decide to take this approach once the summer hits, here's what you have to remember: if you forget to close your windows and blinds on just one hot day, you're pretty much done for. Once the apartment or house gets hot, you can't get it cool again until there is cool air outside.