Why "Cloud Cover Percentage" Is Misleading
Most weather apps report a single total cloud cover number: 40%, 70%, 90%. That number averages cloud coverage across all atmospheric levels into one figure, which loses nearly all the information you actually need as a photographer. A sky with 60% thin high cirrus is completely different from a sky with 60% low stratus. The cirrus lets sunlight through and can paint itself in brilliant colour at sunset. The stratus blocks everything and gives you flat grey light all day.
The atmosphere has three distinct cloud zones: low (below roughly 6,500 feet), mid (6,500 to 20,000 feet), and high (above 20,000 feet). Each zone produces different cloud types with different optical properties. Understanding which zone is active, and how thick the coverage is in that zone, is what actually determines whether you should drive to a location or stay home.
"A single cloud cover percentage collapses three layers of atmosphere into one number. That number is almost useless for photography planning."
Low, Mid, and High Cloud: What Each Does to Light
Cloud Cover for Golden Hour and Sunset
The most dramatic golden hour and sunset conditions combine two things: enough cloud at mid to high altitude to catch and reflect colour, and a clear gap near the horizon that lets direct light in. The cloud is the canvas; the horizon gap is the light source. When both exist simultaneously, you get colour that extends across the entire sky, not just at the horizon.
Cloud Cover for Astrophotography
Astrophotography has zero tolerance for cloud. Even thin, nearly invisible cirrus at high altitude reduces contrast and washes out faint stars and Milky Way structure. The total cloud cover number in a standard weather app doesn't capture this — a 5% cloud cover forecast can still have enough thin high cirrus to ruin a Milky Way shot.
For serious night sky work, you need each layer to be clear: low, mid, and high. Check them separately if your forecast source provides that breakdown. Atmospheric transparency — a measure of how clean the air column is from turbulence and aerosols — is a separate variable from cloud cover and also affects the quality of night sky images. Clear skies over a location with poor transparency (smoke, pollution, high humidity) still produce degraded star images.
Total cloud cover under 10%, with no cirrus visible. Atmospheric transparency: good to excellent. Seeing (atmospheric turbulence): average or better for wide-field Milky Way work; good to excellent for planetary or star detail. Check all three independently.
When Overcast Is Actually the Right Call
Overcast conditions are genuinely superior for several categories of photography. A cloudy day is not a failed shoot day — it's often the optimal condition for subjects that suffer under harsh direct light.
Haze, Atmospheric Diffusion, and Light Penetration
Haze is distinct from cloud cover, and standard weather apps typically don't surface it. Haze comes from aerosols in the atmosphere: humidity, dust, smoke, and urban pollution. Even on a clear day with 0% cloud cover, significant haze can reduce colour saturation, lower contrast, and cut the effective range of telephoto compression dramatically.
The most common scenario is summer haze: high humidity combined with warm temperatures creates an atmospheric moisture layer that looks clear at ground level but shows up as a white veil in photographs of distant subjects. Telephoto shots of mountain ranges, compressed city skylines, and wide-angle landscape shots with visible distance all suffer most from haze.
The simplest field test: look at the farthest visible object from your location. If detail is visible clearly to the horizon, atmospheric transparency is good. If distant ridgelines or buildings are softened or invisible, haze is present. After a rain event, rain-scrubbed air produces some of the clearest conditions of the year — plan shoots for the day or two following significant precipitation.
Smoke from wildfires adds a specific signature: a warm orange-red cast across the entire sky, reduced blue channel, and an overall compression of dynamic range. In small amounts, smoke haze can add a dramatic, moody quality to golden hour shots. At higher concentrations, it degrades the image quality significantly and can eliminate sunsets entirely by scattering the light before it reaches the horizon at a useful angle.
CloudCast: Cloud Scoring by Shooting Target
Reading low, mid, and high cloud layers separately, then factoring in haze and light penetration, is a lot to check manually before every shoot. CloudCast, exclusive to the LightCast iOS app, does this automatically. It pulls hourly cloud data at all three atmospheric levels, calculates light penetration and shadow strength, factors in atmospheric haze, and scores the sky specifically for your shooting target: golden hour, landscape, portrait, or astrophotography.
A golden hour CloudCast score weights mid-level broken cloud and horizon clarity heavily. An astrophotography score penalizes any cloud at any level, including thin high cirrus that standard forecasts don't flag. The score changes as you switch targets — the same sky can be excellent for portraits and completely wrong for night sky work.
Common Questions About Cloud Cover and Photography
Is cloud cover good or bad for photography?
It depends entirely on what you're shooting and which cloud layer is active. High cirrus at golden hour often improves colour. Complete low stratus kills it. Overcast is excellent for waterfalls, forests, and portraits. For astrophotography, any cloud is bad. The single percentage number from a weather app doesn't tell you which situation you're in.
What percentage of cloud cover is best for golden hour?
For the most dramatic golden hour, 30 to 70% coverage at mid levels (altocumulus or altostratus), with a clear band near the horizon. The cloud catches and reflects colour from below while direct light enters through the horizon gap. Zero percent can produce clean golden light but limits sky drama. Above 80% low cloud usually means no usable direct light at all.
Does haze show up in cloud cover forecasts?
No. Haze is an aerosol condition, not a cloud condition. A forecast can show 0% cloud cover and still have significant haze from humidity, dust, smoke, or pollution. They need to be checked separately. The most reliable indicator of good atmospheric transparency is the period immediately after significant rainfall.
What clouds make the best sunsets?
Altocumulus and altostratus at mid altitude produce the most vivid sunset colour. They sit low enough to be illuminated directly by the sun below the horizon and high enough to stay lit for 10 to 30 minutes after the sun sets. High cirrus spreads colour more diffusely over a larger area. Cumulonimbus towers can produce dramatic vivid pink and orange vertical structure when backlit. Low stratus almost always blocks the sunset entirely.
Can I photograph the Milky Way with any cloud cover?
With thin cirrus, you'll see a degraded result: reduced contrast, washed-out faint star field, Milky Way core visible but detail lost. With mid or low cloud at even 20%, you won't see it at all through the covered portions of the sky. For Milky Way work, treat cloud cover as a binary: all layers clear, or don't go. Check low, mid, and high cloud separately if your forecast source provides that data.