Birds can become accustomed to a wide range of temperatures, although it seems to me that some parrots can handle cooler temperatures better than they can handle warmer temperatures.
I have taken Charlie, my mitred conure outside in below freezing temps for short periods of time before and he did fine. Didn't seem crazy about the snow, though!
Indoor temps for my birds can range anywhere from the 50's to the 80's, sometimes even warmer. In the summer time I like to keep the window(s) open 24/7, so the temperature of the room can vary depending upon the temperature of outside. (then again, the house is not kept at an even temperature through-out the year, windows open or not!)