Perseids meteor shower 2010 | Video courtesy of "meteorlog"
According to Wikipedia, during the peak, the rate of meteors reaches 60 or more per hour. They can be seen all across the sky, but because of the path of Swift-Tuttle's orbit, Perseids are primarily visible in the northern hemisphere. As with all meteor showers, the rate is greatest in the pre-dawn hours, since the side of the Earth nearest to turning into the sun scoops up more meteors as the Earth moves through space.
The Perseid meteor shower occurs every year and is visible starting mid-July. It peaks on August 9 and 14, depending on the particular location of the stream.