Sky Color, Clouds, and the Best Times of Day to Photograph

Colorful sunrises and sunsets are exciting. As our day winds down, a colorful sunset sky above gives us pause to stop and look around.

Whether or not this morning’s sunrise will be stunning or a dud is low on most people’s priority list. As nature photographers, we strive to photograph beautifully colored skies and landscapes. We need to set up our tripods in a scenic location before the magical light begins. How can we know when the sunrise or sunset will be good?

Since getting up well before dawn and situating ourselves in an ideal spot requires fortitude and lots of coffee, we prefer to reduce the guesswork on whether or not we stay in bed or do the hard work for a chance of excellent morning sky.

We can improve our photography by understanding why the sunrise and sunset sky colors vary. Armed with this knowledge, you will be able to anticipate when beautiful skies will occur.

I genuinely enjoy looking at the sky conditions each day and seeing how well I can predict the sunset show.

Sunset over the Jemez Mountains in New Mexico. When the low angle and warm-colored light at dawn and dusk can illuminate the undersides of clouds, they become red. The shadow of the mountain range is seen on the virga.

Photograph Before the Sun Rises and After the Sun Sets

The visible light from the Sun is composed of all colors and is therefore white.

Air molecules and microscopic particulates in the Earth’s atmosphere scatter sunlight. Light scatters in all directions from air molecules, including back towards the Sun.

This type of scattering is called Rayleigh scattering, named after John William Strutt (3rd Baron Rayleigh, or Lord Rayleigh), who explained in 1871 how particles smaller than the wavelength of light elastically scatter light. Lord Rayleigh was the first to explain how this type of diffuse scattering is responsible for the sky being blue and sunrises/sunsets being red.

The shorter wavelengths of light (violet and blue) scatter more efficiently than the longer wavelengths (orange and red). The longer the path length that sunlight travels through the atmosphere, the more scattering occurs. The sky would be purple since purple is a shorter wavelength than blue if the spectrum of sunlight was uniform. Since the solar spectrum falls off in the purple-violet, and oxygen in the atmosphere absorbs purple-violet light, the dominant color for Rayleigh scattering is blue. Our vision is less sensitive to purple than blue.

Since blue scatters more than the warmer colors, blues and purples are essentially removed from the sunlight rays over a long enough distance through the atmosphere, leaving the light rays from the Sun to be orange-red.

For long path lengths through the atmosphere, blue light is removed by scattering, leaving the warmer colors (yellow, orange, red). We can notice those warm colors when the low-angle sunlight reflects off a cloud or distant mountain.

Warm colors of scattered sunlight illuminate the underside of clouds and snow-capped peaks in the Sangre de Cristo Mountains near Santa Fe. The name “Sangre de Cristo” (“Blood of Christ” in Spanish) is based on the red color they frequently display near sunset, especially when covered with snow.

Civil twilight light illuminates the undersides of clouds. The dark rays are shadows from distant mountains. Notice the gap under the clouds on the horizon. If sunlight can pass underneath the cloud layers on the horizon, the warm-colored sunlight can illuminate the bottoms of the clouds above you. Bosque del Apache National Wildlife Refuge, New Mexico.

Sunrise light and mountain shadow at the Bosque del Apache National Wildlife Refuge

The amount of Rayleigh scattering of sunlight in the atmosphere as a function of wavelength (color) is shown here. Rayleigh scattering occurs when the scattering particles (molecules and aerosols in the air) are very small compared to the wavelength of light.

Forecasting the Sky Color

Clouds are an Important Ingredient for a Colorful Sky

If you pay attention to clouds on the horizon you can make reasonable predictions on how colorful the sky will be around sunrise or sunset.

When the low-angle reddened rays of sunlight illuminate the undersides of clouds they reflect the colorful sunlight towards our eyes.

Low clouds on the same horizon as the rising or setting Sun can block these low-angle sun rays, resulting in flat light and a gray sky.

If there is a gap between the bottom of the clouds and the horizon where the Sun is rising/setting the sky lighting can be incredible. We refer to this as “gap light.”

Clearing storms at sunrise or sunset are good conditions to experience gap light and phenomenal lighting.

For sunset, look to the western horizon to check if clouds will block the low-angle sunlight. If I see a gap underneath the clouds on the horizon, I am more confident that beautiful sky color is likely to occur.

Skyfire is a useful (paid) app that forecasts the color of the sky around the times of sunrise and sunset. Skyfire uses near-real-time data on cloud ceiling heights and clouds on the horizon to predict sky color around sunrise/sunset. It is fairly accurate and I use it frequently to plan my landscape shots. Skyfire is available as an add-on to the TPE app on IOS or is available as a separate app for Android phones. Skyfire is not yet available as a web app.

Gap light at evening twilight over Cerro Pedernal, New Mexico.

The Skyfire app shows the forecast for sky color at sunrise on a stormy morning in the Santa Fe area. The white areas indicate clouds. Blue indicates a 50% probability of red sky colors; orange areas indicate a 75% probability of warm sky colors, and red areas indicate a 100% probability of warm sky colors.

Skyfire forecasts for sky color around sunset for the same stormy day in the Santa Fe area. The forecast looks promising for sky color to the west of Santa Fe at sunset — which makes sense since the storm will be clearing by then, allowing the low-angle red sunlight to shine below clearing cloud layers to the west.

The settings page for the Skyfire app is shown here. It is helpful to refer to this page to see the time of the most recent forecast. Skyfire forecasts the sky color for the current and two days out (Skyfire Basic), or four days out (Skyfire Plus). The forecast for the current day is updated every hour.

When Skyfire forecasts an area with a high probability of having colorful lighting it means that if you stood underneath the clouds in that area they would be colorfully lit. You will however often be able to see the same colorful clouds when you are not directly underneath them, for example when they are above a distant horizon. In the Skyfire forecast for sunset, shown in the middle screenshot above, the photographer in Santa Fe would see a colorful sky and underlit clouds to the west, over the Jemez Mountains.

A Skyfire Plus subscription allows you to set push notifications for your favorite locations when the forecast predicts colorful skies in your favorite locations. I find this handy to give me a heads up when the sky color forecast is good for my local area.

The Twilights

When the Sun is below the horizon, and there is some light in the sky, it is twilight. Twilight ends when the Sun is above the horizon.

During astronomical twilight, the atmosphere scatters some sunlight into the dark sky, making the fainter celestial objects harder to see. The elevation of the Sun during astronomical twilight is between [-18°,-12°]. During astronomical twilight, we cannot see objects on the horizon.
We can see the silhouette of objects on the horizon and some stars and planets during nautical twilight (allowing for nautical navigation). The center of the Sun has an elevation angle of [-12°,-6°] during nautical twilight.
We can carry out most activities during civil twilight, the brightest of the twilights. In the morning, civil twilight starts when the center of the Sun is 6 degrees below the horizon and ends when the top of the Sun touches the horizon. The elevation of the Sun ranges from [-6°,-0.25°]. Note the angular size of the Sun is 0.5°. The evening civil twilight starts when the top of the Sun’s disk sinks below the horizon and ends when the Sun is 6 degrees below the horizon.

The twilights are good times to photograph, especially when layers of clouds are in the sky. When the colorful twilight rays from the Sun illuminate the underside of clouds and reflect to our eyes, stunning light occurs.

To find times of the twilights in your location, please use The Photographer’s Ephemeris web app or smartphone app. You can also use TimeAndDate.com website to plan your twilight photography.

Morning Twilights

The morning twilight periods, especially nautical and civil twilight, are great times to photograph landscapes and cloudscapes.

Morning twilight colors are often best when stormy weather is approaching.

Red sky at night, sailors’ delight.
Red sky at morning, sailors’ warning.

This famous saying is accurate in the northern hemisphere, where most storm systems approach from the southwest. When a storm is approaching, the rising morning Sun in the east can light the undersides of the incoming storm clouds, resulting in a red sky.

A red sky can also be seen to the east of your location when red sunlight rays light the underneath of clouds beyond the eastern horizon. You see those bright red colors in the distant sky since the clouds are high altitude.

Stunning colors before sunrise in Monument Valley, a widespread storm hit the area later that afternoon. The view here is looking east, towards the rising sun.

Beautifully colored sunrise over Monument Valley.

The morning twilights are shown here with their precisely defined elevation angles of the Sun. The best cloud and sky photography often occurs during nautical twilight and civil twilight – when the Sun’s elevation angle is negative, meaning it is below the horizon. The “blue hour” and “golden hour” do not have a precise definition when it comes to the Sun’s elevation angle, the most widely accepted views are that the blue hour occurs when the Sun’s elevation angle is between [-6°,-4°], and the golden hour the Sun’s elevation is considered to be [-4°,+6°], although The Photographer’s Ephemeris defines the golden hour as [0°,+6°]. Neither the blue hour nor golden hour lasts an hour at most latitudes unless you are far north.

Evening Twilights

Evening twilight periods, after sunset, are great times to photograph. I find that clearing storms, especially in the summer when the clouds from afternoon thunderstorms begin to dissipate, result in great conditions for sky colors.

The famous saying below once again gets it right.

Red sky at night, sailors’ delight.
Red sky at morning, sailors’ warning.

When storms are clearing, the southwesterly direction they generally move in allows for the warm-colored sunlight to illuminate their undersides. I pay particular attention to the western horizon to ensure the sunlight is not blocked to the west of my location.

Evening twilight color, after the sun has set, over Cerro Pedernal, New Mexico. Note the clearing winter storm as indicated by the virga and the ability for the low angle sunrays to illuminate the underside of the clouds. This view is looking west after the sun has set.

The three evening twilights are shown here with their precisely defined Sun elevation angles. The best cloud and sky photography often occurs during nautical twilight and civil twilight – when the Sun’s elevation angle is negative, meaning it is below the horizon. The “blue hour” and “golden hour” have a vague definition when it comes to the Sun’s elevation angle, the most widely accepted views are that the blue hour occurs when the Sun’s elevation angle is between [-4°,-6°], and the golden hour is [6°,-4°]. However, The Photographer’s Ephemeris considers the golden hour [+6°,-4°]. Neither the blue hour nor golden hour lasts an hour at most latitudes unless you are far north.

The Blue Hour

During nautical twilight, when the Sun is far enough below the horizon, the remaining sunlight can be a deep blue in color. This deep blue color is different from the color of the blue sky on a clear day when the Sun is above the horizon. The cause of the deep blue color during the “blue hour” period is the absorption of warmer colors by ozone in the upper atmosphere. This phenomenon is different from Rayleigh scattering of blue wavelengths in the atmosphere that causes red skies closer to sunrise and sunset.

The “blue hour” lacks any precise definition based on the solar altitude or elevation angle of the Sun. The colloquial term “blue hour” refers to this period during part of nautical twilight when the sky is deep blue before sunrise and after sunset. The most popular estimate for the blue hour is when the Sun is at an elevation angle between [-6°, -4°], although you will also find it informally defined as [-8°,-4].

Photography during the blue hour can be magical, especially when there are artificial lights from distant cities or planets accent the blue sky.

Lighting and house lights look great during this blue hour photograph.

The Belt of Venus and the Earth’s Shadow

When the Sun is below the horizon during civil twilight, sunlight reddened from Rayleigh scattering in the atmosphere, backscatters from fine particulates and air molecules in the upper atmosphere. The backscattered light shows up as a pink band of light above the horizon opposite from the Sun. This pink band is named “The Belt of Venus” or the “anti-twilight arch.”

Below the Belt of Venus is a dark blue region, This area is devoid of backscattered light. It is the shadow of the Earth cast onto the upper atmosphere and space and is referred to as “The Earth’s Shadow.”

When there are no clouds in the sky, especially on cold winter days, photographs of the Belt of Venus above the landscape can be spectacular. Look for mornings when the setting moon can be photographed in the Belt of Venus.

The name, “Belt of Venus”, is unfortunate since the planet Venus is never seen in the Belt of Venus. Venus is an interior planet, meaning its orbit is closer to the Sun than Earth’s orbit. Since Venus is an interior planet we never see it opposite the Sun, and since the Belt of Venus is always opposite the Sun, Venus is never seen in the Belt of Venus. So then, why is it called the “Belt of Venus”?

The name has nothing to do with the planet, Venus. The pink band was originally thought to be a girdle or breast-band of the Ancient Greek goddess Aphrodite, who is often equated with the Roman goddess Venus. The “Belt of Aphrodite” would be a more appropriate name for the pink glow.

Full moon setting in the pink glow of the Belt of Venus. The darker blue region below the Belt of Venus is the shadow of the Earth as seen on the outermost atmosphere and space.

Belt of Venus over Windy Mountain, San Juan Mountains, Colorado

The Golden Hour

Photographers refer to the period when the Sun’s elevation is between [-4°,+6°] as the “golden hour.” During this period, which is less than an hour, unless you are at very high latitudes (i.e. by the arctic circle), the landscape is lit by indirect sunlight. Indirect light is less harsh than direct sunlight — where the shadows are dark and the highlights are very bright. When the Sun is in the “golden hour” it is hard to overexpose or underexpose an image since the soft and indirect light is very even. The atmosphere diffuses and softens the sunlight during the golden hour.

Since the sun is at a low angle in the sky during the golden hour shadows are elongated and desirable in landscape photography. The low angle and soft light provide the photographer with creative effects such as side lighting, silhouettes, sunburst, and backlighting.

The low-angle path sunlight travels through the atmosphere during the golden hour resulting in more Rayleigh scattering resulting in warmer light with lots of yellows, oranges, and reds — creating images that convey happiness and warmth.

You need to move quickly when photographing during the golden hour. The low-angle sunlight quickly changes the lighting of the landscape. Take lots of photos during the golden hour and plan ahead so you are not changing lens, memory cards, or batteries during the golden hour and rapidly changing light.

Sandhill cranes in the golden hour morning light at the Bosque del Apache National Wildlife Refuge, New Mexico.

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