Forecasting the light: golden hour, cloud and clear breaks

Every app knows what time the sun sets. That is astronomy, and it is not the hard part. What decides whether a sunset is worth driving for is the cloud in the hours around it — and specifically whether there is a clear gap near the horizon for light to come through underneath the cloud.

The quick answer

• A completely clear sky makes a plain sunset. No cloud, nothing to light up.
• Complete overcast makes a flat grey one. The light never reaches the underside.
• Broken or scattered high cloud with a clear gap low in the west is the good case — the sun drops below the cloud deck and lights it from beneath.
• Read the hours before, not the minute of. Cloud arriving an hour early kills it; cloud clearing an hour early makes it.
• In Weathergraph the cloud strip runs along the top of the hourly chart with a glow over daylight hours that are clear or mostly clear, so the shape of the afternoon's cloud — and any break in it — reads at a glance. Sunrise and sunset sit in the details card below.

What kind of cloud makes the light

Cloud in the hour before sunset	Likely result
Clear, 0–10%	Clean gradient, no colour. Good for silhouettes, not for drama.
High, thin, 20–60%	The best case. High cloud catches colour long after the sun is down.
Broken mid-level with a clear western horizon	Strong, brief colour as the sun slips under the deck.
Overcast to the horizon	Flat. The light stays grey.
Thick low cloud clearing late	Worth waiting — the gap often opens after the official sunset time.

The general rule: colour needs something to land on, and a path for the light to reach it. Both halves have to be true, which is why "partly cloudy" is a better forecast for a photographer than either extreme.

Golden hour is a window, not a moment

The usable light runs from roughly the last hour before sunset to twenty minutes or so after, and the best of it is often after the sun has gone. That is when the underside of any cloud lights up. Plan to still be there fifteen minutes after you would otherwise have packed up.

The same is true in reverse at dawn, with one addition: clear, calm nights frequently end in valley fog, which is either the shot of the morning or the thing that hides it entirely. The mechanism is in our guide on why clear nights end in fog.

Reading the afternoon to predict the evening

1. Look at the cloud strip across the whole afternoon, not just at sunset. A clearing trend is more promising than a snapshot.
2. Check whether precipitation ends before sunset. A clearing shower often leaves exactly the broken cloud that makes the light.
3. Check wind. Strong wind moves the cloud faster than the forecast resolution — good for a gap opening, bad for planning a long exposure.
4. Have a second location. The cheapest insurance against a forecast that shifts by an hour.

For night work

If the plan is astro rather than golden hour, the question changes from "is there interesting cloud" to "is there any cloud at all", and moonrise matters as much as clear sky. Our guide on finding a clear-sky window for stargazing covers that case.