Sky watchers are gearing up to view the Geminid meteor shower, which astronomers consider one of the best and most reliable of the 30 or so annual meteor showers. This year the Geminids peak late Tuesday night into early Wednesday morning—though light from a waning gibbous moon is expected to wash out fainter meteors.

“The moon’s a bummer,” said Bill Cooke, lead astronomer for the Meteoroid Environment Office at the National Aeronautics and Space Administration’s Marshall Space Flight Center in Huntsville, Ala. The moon will be about 75% illuminated on the night of the shower’s peak, he added.

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Weather permitting, sky watchers in the Northern Hemisphere will likely glimpse 30 to 40 meteors an hour during the peak this year, according to Dr. Cooke. That is down from about 150 an hour during the peak when the skies are dark and viewing conditions are optimal.

The Geminids will reach peak rates at 5 a.m. Eastern Time on Wednesday, though meteors should be visible starting late Tuesday night, according to NASA. To minimize interference from moonlight, consider heading out for a look before moonrise, about 10 p.m. local time, said Anna Gammon-Ross, an astronomer at Royal Museums Greenwich in London.

For the best viewing, find a dark place away from city lights. Lie on your back with your feet facing south. Positioning yourself so that an object—like a house or a tree—blocks direct light from the moon can boost your chances of seeing the meteors, Dr. Cooke said.

It will take about 30 minutes for your eyes to adjust to the darkness. Leave your cellphone in your pocket, as its light will impede that adjustment. And there is no need for binoculars or a telescope, as they will limit your view to only a small portion of the sky at a time.

Meteor showers occur when fast-moving bits of debris left behind by a comet or asteroid strike Earth’s atmosphere. In the case of the Geminids, Earth is moving through debris from 3200 Phaethon, a space rock that was discovered in 1983. When the dust and debris from 3200 Phaethon hit the atmosphere at speeds of about 78,000 miles an hour, they burn up, superheating the air around them and leaving streaks in the sky.

The Geminids are named for the Gemini constellation, which lies in the region of the sky from which the meteors appear to originate.

Write to Aylin Woodward at aylin.woodward@wsj.com