The annual Lyrids usually are quite modest as showers go, with peak hourly rates of 15 to 20 meteors. But the celestial event is known to produce surprises on rare occasions, making them worth watching, astronomers say. (Read about last year's Lyrids.)

"Brief outbursts of around a hundred meteors per hour have been noted a couple of times in the 20th century, and Chinese astronomers in 687 B.C. recorded Lyrid meteors falling like rain overhead," said Mark Hammergren, an astronomer at Adler Planetarium in Chicago, Illinois.

These unusual outbursts occur when Earth passes through a particularly dense stream or clump of debris in the comet's orbit, he said.

Lyrids are known to produce bright, fast-moving meteors, with about 15 percent leaving