SKY · FIELD GUIDE
Is Tonight Good for Stargazing? How to Read the Conditions
You've got a free evening and a clear-ish sky — but is it actually worth driving out to stargaze tonight? Three things decide it, and you can check all of them in a couple of minutes.
Stargazing rewards planning more than almost any hobby, because the difference between a magical night and a wasted drive comes down to a few conditions you can check in advance. The good news: there are really only three of them, and they sort neatly in order of importance.
1. Cloud cover — this is the whole game
No amount of darkness saves an overcast sky. Cloud is the single biggest factor in whether tonight is worth it, so it's always the first thing to check. The trick is to look at the cloud forecast across the hours you'll actually be out, not just the reading for right now — skies clear and close over through the night, and a "partly cloudy" evening can turn into a flawless midnight or vice versa.
That's why the rating on these pages uses the average cloud cover over tonight's dark hours, from sunset to sunrise, rather than a single snapshot. Under roughly 15% cloud is a superb night; up to about 35% is still good with the odd passing cloud; once you're past 60% you're waiting for breaks; and above 85% it's usually not worth it.
2. The Moon — friend to planets, enemy of faint skies
The Moon is the second big lever, and it cuts both ways. A bright Moon is wonderful to look at — and it doesn't bother the bright planets or the brightest constellations one bit. But it floods the whole sky with light, and that erases everything faint: the Milky Way, meteor showers, faint star clusters and galaxies all vanish under a gibbous or full Moon.
So match your target to the Moon. Want to see the Moon's craters, Jupiter's moons or Saturn's rings? Any clear night works. Chasing the Milky Way or a meteor shower? Plan for the week either side of a New Moon, when the sky is at its darkest.
3. True darkness — and when there isn't any
The third factor only bites at high latitudes, but it's worth knowing. Genuine "astronomical darkness" needs the Sun to sink well below the horizon. Near midsummer in far-northern (or far-southern) places, it never does — the sky stays in a permanent blue twilight all night, and faint stars simply never come out. Our city pages are honest about this: if a location gets no true dark tonight, they say so rather than pretend.
Putting it together
A great stargazing night is clear + dark + Moonless — and the rating combines all three into one plain verdict for your location, along with what's realistically worth looking for. Cloud sets the ceiling (an overcast sky can't be rescued), the Moon decides whether faint targets are on the table, and the darkness window tells you the hours to aim for.
One last thing the conditions don't cover: how dark your site is. That's light pollution — a fixed property of where you stand, not of tonight's weather — and it decides how many stars you'll see once the sky is clear. Pair a good-conditions night with a trip to a genuinely dark site, and you'll see a sky most people never do.
Frequently asked questions
What matters most for a good stargazing night?
Cloud cover, by a wide margin. A perfectly dark, Moonless sky is worthless if it's overcast, while even a brightly-lit suburb can show the Moon and bright planets on a crystal-clear night. So the first thing to check is the cloud forecast across the hours you'll actually be out — not just the moment you step outside. After cloud comes the Moon, and then how dark your site is.
How does the Moon affect stargazing?
A bright Moon floods the sky with light and washes out anything faint — the Milky Way, meteor showers, faint star clusters and galaxies all disappear. The brightest stars, the planets and the Moon itself are unaffected. So a Full Moon is great for looking at the Moon and planets but poor for deep-sky observing; the week either side of a New Moon is best for faint targets.
What is 'astronomical darkness' and why does it matter?
It's when the Sun is more than 18 degrees below the horizon and the last of twilight is gone, leaving the sky as dark as it gets. In the weeks around midsummer at high latitudes — places like Reykjavík, Stockholm or the north of Scotland — the Sun never drops that far, so the sky stays in permanent twilight all night and faint objects never appear. Our city pages tell you honestly when a location gets no true darkness.
What's a good cloud-cover number to aim for?
Under about 15% cloud over your viewing window is excellent; up to roughly 35% is still a good night with a few passing clouds; 35–60% means patient, broken viewing; and above about 85% there's little point. We use these same bands in the live reading so the forecast and the verdict always agree.
Does light pollution change the verdict?
It changes what you can see, not whether the sky is clear. A clear, Moonless night in a city is still a clear night — you'll just see far fewer stars than someone at a dark-sky site. We treat tonight's conditions (cloud, Moon, darkness) as the live rating, and how dark your site is (light pollution) as separate context, with real dark-sky destinations near your city on the light-pollution pages.
How far ahead can I trust a stargazing forecast?
Cloud forecasts are reliable a day or two out and get rougher beyond that, so treat anything past tomorrow night as a rough steer and check again on the day. The Moon phase and darkness window, by contrast, are pure astronomy — they're known precisely for any night, years ahead.
SEE IT LIVE
Everything in this guide is on the live sky map.