The ideal bedroom temperature is between 60 and 67 degrees, according to the National Sleep Foundation. So, what should you do if you don't have AC ? "You buy an AC, that's what you do," Dr. Ebben says. While that's not economically feasible for everyone, there are some very good reasons why you should have an AC , especially if you live in an apartment in New York City. Last summer, a study conducted by WNYC found that while the air outdoors will cool down at night, the temperature inside of apartments tends to stay as hot as it was during the day, so if you don't have AC, it can feel like you're sleeping during the heat of the day.