Comet Swift-Tuttle made its most recent appearance more than 20 years ago, in December 1992. Its orbit is highly elongated and as such it takes roughly 130 years to make one trip around the sun.
For several years before and after its 1992 return, the Perseids were a far more prolific shower, appearing to produce brief outbursts of as many as several hundred meteors per hour, many of which were dazzlingly bright and spectacular. The most likely reason was that the Perseids parent comet was itself passing through the inner solar system and that the streams of Perseid meteoroids in the comet's vicinity were larger and more thickly clumped together, leading to brighter meteors as well as much-higher-than-normal meteor rates.
But now, with the comet now having retreated nearly 3.2 billion miles (5.1 billion km) back out into space, Perseid activity has returned to normal.
Perseid meteor clumps
A very good meteor shower will produce about one meteor per minute for a given observer under a dark country sky. However, any light pollution from city lights or moonlight considerably reduces the count.
The August Perseids are among the strongest of the readily observed annual meteor showers, and at maximum activity nominally yield 90 or 100 meteors per hour. However, observers with exceptional skies often record even larger numbers.
But while 90 to 100 meteors per hour correspond to at least one meteor per minute, keep in mind that this is only a statistical average. In reality, what usually is seen is what some have called, "the clumping effect." Sometimes you'll see two or even three Perseids streak across the sky in quick succession, all within less than minute. This is usually followed by a lull of several minutes or more, before the sky suddenly bears fruit once again.
When and where to look
Typically during an overnight watch, the Perseids are capable of producing a number of bright, flaring and fragmenting meteors, which leave fine trains in their wake. On the night of shower maximum, the Perseid radiant is not far from the famous "Double Star Cluster" of Perseus.
Low in the northeast during the early evening, it rises higher in the sky until morning twilight ends observing. Shower streakers appearing close to the radiant have foreshortened tracks; those appearing farther away are often brighter, have longer tracks, and move faster across the sky. About five to 10 of the meteors seen in any given hour will not fit this geometric pattern, and may be classified as sporadic or as members of some other (minor) shower.
Perseid meteor shower activity increases sharply in the hours after midnight, so plan your observing times accordingly. We are then looking more nearly face-on into the direction of the Earth’s motion as it orbits the sun, and the radiant is also higher up.
Making a meteor count is as simple as lying in a lawn chair or on the ground and marking on a clipboard whenever a "shooting star" is seen. Watching for the Perseids consists of lying back, gazing up into the stars, and waiting. It is customary to watch the point halfway between the radiant (which will be rising in the northeast sky) and the zenith, though it's all right for your gaze to wander.
Meteor counts should be made on several nights before and after the predicted maximum, so the behavior of the shower during off-peak nights can be determined. Usually, good numbers of meteors should be seen on the preceding and following nights as well. The shower is generally at one-quarter strength one or two nights before and after maximum.