The answer depends on five things you can check right now.
A good stargazing night comes down to five measurable conditions: cloud cover, moon brightness, wind speed, humidity, and how dark the sky actually gets. You don't need perfect conditions for every type of observing — planets are visible even through thin cloud and moonlight, while faint deep-sky objects demand clear, dark, calm skies.
Cloud cover matters most. Even 30% cloud means a third of the sky is blocked, and for visual observing that's the difference between a frustrating session and a rewarding one. Low clouds (below 2,000m) block everything; high cirrus clouds at 6,000m+ are thinner but still scatter light and reduce contrast on faint objects.
Wind is the second factor most beginners overlook. Anything above 15 m/s makes a telescope unusable — the image shakes constantly, and even binoculars become difficult to hold steady. Wind also drives atmospheric turbulence (what astronomers call "seeing"), which blurs planetary detail even when skies are otherwise clear.
Humidity above 80% causes dewing on optics. You'll spend more time wiping eyepieces than observing. It also degrades atmospheric transparency, making the sky appear washed out even when technically cloud-free.
The moon is a double-edged factor. A bright moon (illumination above 60%) floods the sky with light, washing out the Milky Way, faint nebulae, and galaxies. But if you're observing the moon itself, or bright planets like Jupiter and Saturn, high illumination doesn't matter at all. This is why Clear Skys offers observer profiles — an astrophotographer penalises moonlight heavily, while a planetary observer barely notices it.
Clear Skys calculates an hourly score from 0 to 100 for every hour of darkness at your location. Each hour is scored on four weather factors with different weights: cloud cover accounts for 55% of the score, wind speed 20%, humidity 15%, and rain probability 10%. These weights reflect how much each factor actually affects your ability to observe.
The hourly scores are averaged across the full darkness window (the period when the sun is below −18°, known as astronomical darkness). A moon penalty is then subtracted based on how bright the moon is and how long it's above the horizon during your observing window. The result is a single number that tells you, at a glance, whether it's worth setting up tonight.
A score of 80 or above means excellent conditions — clear skies, low wind, manageable moon. Between 65 and 79 is good — you'll have a productive session. Between 45 and 64 is mixed — there will be usable windows but expect interruptions. Below 45 is poor — save your energy for a better night.
The score also identifies your best viewing window: the longest continuous stretch of hours scoring above 65. This is the single most useful piece of information for planning — it tells you exactly when to set up and when to pack away.
Read the full scoring methodology →Light pollution is the permanent background factor that the weather forecast can't change. A perfectly clear, moonless night in central London (Bortle 8–9) will never match a mediocre night at a dark-sky site like Cherry Springs or Galloway Forest (Bortle 2–3).
The Bortle scale runs from 1 (pristine dark sky) to 9 (inner-city sky glow). At Bortle 5 and above, the Milky Way is invisible or barely visible. At Bortle 3 and below, the sky is dark enough to see structure in the Milky Way, the zodiacal light, and hundreds of deep-sky objects.
For most people, the practical advice is: check your forecast, and if conditions are good (score 65+), drive 20–30 minutes away from the nearest town. That single step typically drops you 1–2 Bortle classes, which has a bigger impact on what you can see than any equipment upgrade. Each city forecast page on Clear Skys links to a light pollution map centred on that location so you can find nearby dark spots.
If you're at latitudes above roughly 50°N (the UK, Scandinavia, southern Canada, northern Europe), true astronomical darkness disappears for weeks around the summer solstice. The sun never drops far enough below the horizon, and the sky stays a deep blue-grey all night.
This doesn't mean stargazing is impossible — just different. Bright planets (Jupiter, Saturn, Venus, Mars) are still visible. The moon is unaffected. ISS passes are often better in summer because the station catches sunlight against the twilight sky for longer. And the aurora, if active, can still be seen against the twilight background at high latitudes.
Clear Skys handles this with twilight scoring. Instead of marking these nights as "no data," the app scores them based on how dark the sky actually gets. A night where the sun reaches −14° (mid-nautical twilight) is scored with a sky-brightness penalty but still tells you whether clouds and wind will cooperate. A night where the sun barely reaches −9° is left unscored — at that depth, only planets and the moon are realistic targets.
The fastest way to find out if tonight is worth it: search your location on Clear Skys and check the score. You'll see the overall rating, the best viewing window, which planets are visible, whether aurora is possible, and any satellite passes worth catching.
If you don't have a specific location in mind, here are forecasts for some popular stargazing destinations:
Check tonight's stargazing conditions for any location worldwide.
Search your location →Check a stargazing-specific forecast that accounts for cloud layers, not just general weather. Standard weather apps report total cloud cover as a single number, but stargazing depends heavily on low vs. high cloud. Clear Skys uses layered cloud data weighted for astronomical observing — low cloud blocks more light than thin high cirrus.
Yes, but what you can see changes. A bright moon (above 60% illumination) washes out the Milky Way and faint nebulae, but planets, double stars, and the moon itself are great targets. Switch to a Planetary or Visual observer profile on Clear Skys to get a score that reflects this.
After astronomical twilight ends (when the sun is 18° below the horizon) and before moonrise, if the moon is bright. Clear Skys calculates your best viewing window — the longest stretch of high-scoring hours — so you know exactly when to head out.
Limited but still worthwhile. From a city you can observe the moon, bright planets (Venus, Jupiter, Saturn, Mars), double stars, and satellite passes including the ISS. For deep-sky objects like galaxies and nebulae, you'll need to travel to a darker site — even 30 minutes outside the city centre makes a significant difference.