Q: How many stars can a person see at night with the naked eye?
A: Under ideal conditions, about 3,000 stars should be visible at night with the unaided eye, but many factors can reduce this number, including: a full moon (the sunlight reflected from the moon’s surface brightens the entire sky and obscures fainter stars); artificial lights of towns and cities (that’s why the telescopes on Mt. Wilson near Los Angeles are not as effective as they might be); smoke from fires; dust kicked up by wind, and high humidity. And, of course, clouds can block them out altogether.
Source: S. George Djorgovski, associate professor of astronomy at Caltech