The Best Time to Stargaze: Hour, Moon, Season and Weather

The same backyard can look very different from one night to the next. On some nights the sky is full of stars; on others only a few bright ones show. Most of the difference comes from four things you can plan around: how dark the sky has become, where the Moon is, the weather and, to a lesser degree, the season.

Time of night: when it’s truly dark

The sky doesn’t go dark the moment the Sun sets. Sunlight keeps scattering through the upper atmosphere for a long while, and the sky fades in stages. The US Naval Observatory (USNO) defines three stages of twilight by how far the center of the Sun is below the horizon:

• Civil twilight ends when the Sun is 6° below the horizon. The brightest planets and stars appear, but the sky is still blue.
• Nautical twilight ends at 12° below. The horizon becomes hard to see, and most bright stars are out.
• Astronomical twilight ends at 18° below. After that, the USNO says, scattered sunlight is fainter than starlight and the other natural sources of sky light, so the sky is fully dark.

That last point is when stargazing really starts. At most US locations it comes well over an hour after sunset, and the same stages happen in reverse before dawn. The exact times change with the date and your latitude. Around the June solstice, in Alaska and along the far northern edge of the Lower 48, the Sun doesn’t sink far enough below the horizon for the sky to become fully dark at all.

Each city page under tonight shows when twilight ends and how many hours of full darkness you get.

The Moon: the biggest factor you can plan around

A bright Moon brightens the whole sky, not just its own corner. Under a full moon, the Milky Way disappears, faint stars vanish and most meteors are lost. Moonlight is reflected sunlight, and a full moon is a lot of it.

The Moon’s phase also tells you when it’s up. NASA explains that a full moon rises around sunset and stays up all night, while a new moon rises and sets with the Sun and stays out of the night sky. That gives you a simple pattern:

• New moon and the few nights around it: the darkest nights of the month, with no Moon in the sky for most or all of the night.
• Waxing crescent to first quarter: the Moon is up in the evening and sets before or around midnight. The late night is dark.
• Full moon: moonlight all night.
• Last quarter to waning crescent: the evening is dark, and the Moon rises late at night.

NASA’s skywatching FAQ adds that the Moon rises about 50 minutes later each day on average, so its dark window shifts night by night. Our Moon page shows the current phase, and the moon phases guide explains the cycle.

A bright Moon isn’t all bad. It’s a fine time to look at the Moon itself, bright planets and double stars.

Different targets, different hours

Not everything is best at the same time:

• Meteor showers: the American Meteor Society says the best hours are generally from midnight to dawn, when many shower radiants are higher in the sky.
• Northern lights: NOAA’s Space Weather Prediction Center puts the best activity within an hour or two of midnight, though strong storms can be seen from dusk to dawn.
• The space station: visible passes happen within a few hours of sunset or sunrise, NASA notes, when the station is still in sunlight but your sky is dark.
• Mercury and Venus: these appear only in twilight, low in the west after sunset or low in the east before dawn, as NASA’s FAQ explains.
• Mars, Jupiter and Saturn: best around opposition, when they are up all night.

Season

The seasons change two things: how long the nights are and which stars are up.

Winter nights are long, and full darkness arrives early in the evening, which makes stargazing easier to fit in, though it’s cold. Summer nights are short, and in the northern states full darkness may last only a few hours. Each season also brings its own constellations and showers, so the best season is largely a matter of what you want to see and how comfortable you want to be.

Weather: clouds, haze and steadiness

Clouds end a night outright, but other weather matters too:

• Clouds. Even a thin, high layer of cloud hides faint stars and turns city light into a glowing ceiling.
• Haze and humidity. Moisture, smoke and dust scatter light. On a hazy night the sky looks milky, faint stars disappear and light pollution spreads farther.

Check the cloud forecast for your location on the day you plan to go out.

Location still matters

None of this helps much if you’re under bright streetlights. NASA’s skywatching advice is to find a wide-open spot away from city lights, such as a field, a valley or a lakeshore. Our guide to the Bortle scale explains how to judge your sky and find a darker one.

How our sky score works

Every city page gives tonight a score from 1 to 10. It’s a quick way to see whether a night is worth going out for, built from the same factors described above:

• Darkness. A large part of the score comes from how many hours of full darkness the night has with the Moon down. Hours with the Moon up count for less, depending on how much of it is lit.
• Events. Points are added for things worth seeing that night: a major meteor shower at or near its peak, a chance of the northern lights based on NOAA’s Kp forecast, bright planets in the sky, a lunar eclipse or a bright space station pass.
• Clouds. When a cloud forecast from the National Weather Service is available, the score drops as forecast cloud cover rises, and a mostly overcast night scores near the bottom whatever else is happening.

The score is our own interpretation of these data, not an official forecast. The full method, with the weights we use, is on our methodology page.