How Long After Sunset Does It Get Dark?

An image of the Sun setting behind the mountains as seen from pier 56 in Seattle Washington.

How long after Sunset does it get dark? The time it takes to get dark after sunset will vary depending on your location and the time of the year.

Here in the contiguous states of the U.S., the lower 48, it can range from:

• 1 hour and 10 minutes in the Southern States
• 1 hour and 50 minutes in the Northern States

But there is much to understand about what determines the time it takes to get dark after sunset. So let’s take a deeper look into the transition from day to night.

Many outdoor activities require daylight or the darkness of the night. Natural light is as crucial to outdoor photography as darkness is to observing the night sky. Knowing when it becomes dark can be vital for a successful outcome, especially when artificial light is unavailable.

How Long After Sunset Does It Get Dark? An image of Sunset in the southernmost city of Key West, FL. A view out into the ocean.
Sunset in the southernmost city of Key West, FL

Sunset

Sunset is a daily occurrence, with each colorful experience uniquely different, never quite the same as the day before. These spectacular endings to daylight will vary greatly depending on your location, the season, and the current weather during this time of day.

When is it Sunset?

Sunset is when the tip of the Sun’s disk, referred to as the upper limb, has dipped below the horizon in the Western part of the sky and can no longer be seen. At this moment, the Sun has now set.

Even at sunset, there is still light. This part of the day is known as twilight or dusk.

The Golden Hour

An image of boats on the water amongst buoys enjoying the golden hour of sunset.
Key West sunset during the Golden Hour

As the Sun approaches the horizon, it enters a stage of soft natural light many refer to as “The Golden Hour,” which begins at approximately 6º above the horizon, lasting until the Sun’s center reaches 6º below. Its lighting is a perfect time for creative inspiration, photography, contemplation, or evoking a sense of appreciation.

The light from the Sun low on the horizon has to travel through more of the Earth’s atmosphere, resulting in an effect known as Rayleigh Scattering

The gas molecules and particles in this denser part of the atmosphere scatter away the shorter wavelengths of light, the greens, and blues, leaving the longer red and yellow wavelengths as the primary color our eyes perceive. It’s the same effect that makes the sky blue or changes the color of the Moon.

This process gives us the soft golden-yellow streams of light brushed across the horizon everyone happily stands outside to experience. It happens twice daily, once in the morning as the Sun rises from 6º below the horizon to 6º above, then again as the Sun approaches sunset.

The Blue Hour

An image taken in the town of Sligo, Ireland during twilight of the blue hour. Great contrast of the twilight blue sky while town lights reflect onto the Garavogue river.
Sligo, Ireland during the Blue Hour of Nautical Twilight

Much like the golden hour, “The Blue Hour,” or magic hour, is a desirable time for painters, photographers, or just sunset viewers as the sky turns into a distinctive shade of blue, unlike any seen during daylight.

It results from the red and orange wavelengths being absorbed into the upper atmosphere’s ozone, leaving the bluer colors as the primary color perceived by our eyes. It typically happens towards the end of Civil Twilight as the center of the Sun is at 4º ending midway through Nautical Twilight at about 8º.

Understanding the Transitions of Twilight

An illustration depicting the transitions of twilight through the cycle of day and night.
An illustration depicting the transitions of twilight through the cycle of day and night.
**Degrees are not to scale for purposes of illustrating

What is Twilight?

There are two twilight periods, one in the morning before the Sun rises and the other in the evening, which begins once the Sun has set. These periods are known to many as dawn and dusk.

As the Sun moves below the horizon, it continues to shine from an indirect angle filling the sky with refractive light. This remaining light and period of time, while the Sun is absent from the sky, is known as twilight.

It’s a favorite time for many watching colors change as the light fades, transitioning past three phases of twilight until entering the true darkness of night when the geometric center of the Sun is below 18º from the horizon.

The first of three phases is Civil Twilight.

Civil Twilight

an image of Key West waters during the phase of Civil Twilight. Sail boats and buoys in the ocean.
Key West waters during the phase of Civil Twilight

Civil Twilight begins as the Sun disappears below the horizon at 0º and continues until the Sun’s center has reached 6º below. At this time, the surroundings are still easily seen, with no need for artificial lighting.

The horizon is splashed with colors of soft reds, yellows, pinks, and purples as the golden hour is still on full display. Only the brightest stars and objects in the sky, such as Venus the Evening Star, can be seen.

• 0º to 6º below horizon
• Objects and surroundings are easily seen
• No illumination or artificial lighting required
• The Golden Hour is on full display
• Only the brightest celestial objects are visible in the sky

Nautical Twilight

An image overlooking ocean waters during Nautical Twilight as the brightest stars begin to appear.
Nautical Twilight as the brightest stars appear

Nautical twilight begins once the center of the Sun is between 6º to 12º below the horizon. Surroundings are now almost impossible to make out clearly while colors have turned to shades of gray.

The sky is primarily a deep dark blue except near the horizon where the Sun had earlier set has a light reddish orange glow. Opposite where the Sun had set may be black. Stars and constellations are out and easily seen in clear skies.

In the distant past, when sky navigation was more critical, it was at this stage sailors could point out stars for navigation and still reference the horizon, which ultimately inspired this phase to be named nautical twilight.

• Sun’s center is 6º to 12º below the horizon
• Surroundings on the ground are difficult to distinguish
• Artificial lighting is required for outdoor activities
• The sky is mostly a dark blue except black at
the horizon opposite where the Sun had earlier set.
• Constellations and stars are easily seen

Astronomical Twilight

An image of the Nashville riverfront skyline during astronomical twilight.
The Nashville Skyline during Astronomical Twilight

Astronomical Twilight happens once the center of the Sun has cleared 12º below the horizon completing the phases of twilight beyond 18º.

At this period of twilight, many would feel this is night as it is very dark on the ground and surroundings. It’s a good time for stargazing, observing deep-space objects, and it will continue to improve as the night gets darker. The Milky Way can be viewed with the naked eye if you have a clear sky and no light pollution.

• Sun’s center is 12 to 18º below the horizon
• It appears to most as night, very dark
• Illumination and artificial lighting required
• The sky will be black but may be dark blue near where
the Sun had set
• Darkness is sufficient for observing deep space objects

The Night

A view of the ocean during the Night hours with a bright Moon in the horizon.
A view of the ocean during the Night hours

The night is the end of astronomical twilight and the beginning of astronomical dusk. No light from the Sun is reaching any part of the atmosphere in this area of the world.

The complete darkness of nighttime has arrived, with only artificial light visible except for any illumination from the Moon, depending on its phase. It’s the perfect time to be observing the night sky.

Hours will pass, and the phases of twilight will be repeated in reverse as the Sun begins to rise within a new day. Repeating the entire cycle of day to night once again.

How Location and Time of the Year
Impacts Darkness

Latitude, Location, and the Equator

Earth’s sphere shape and the slight tilt of its axis (23.4º) affect how the Sun’s light reaches the Earth’s surface.

Similar to the shape of a ball, the midpoint of our planet between the north and south pole is the most outward and extended area, widest in circumference.

If we draw an imaginary line around this center point of Earth, this line represents what is known as the planet’s equator. It divides the sphere into two parts the northern hemisphere on top and the southern hemisphere on the bottom.

From the equator, both the north and southern hemispheres begin to curve inward toward the poles. At this location of 0º, the Sun rises and sets almost vertically relative to the horizon transitioning through twilight phases more quickly.

The higher the latitude, moving north or south away from the equator, the wider an angle and the slower approach the Sun appears to set and rise in the sky, moving through the total span of eighteen degrees and three phases of twilight. These transitions will take longer for both sunrise and sunset.

Angle Inlet, MN vs. Key West, FL

Spring Equinox | March 20, 2023

Lets look at an example of how latitude affects the time it takes to get dark after sunset.

We’ll compare the northernmost city, Angle Inlet, MN, vs. the southernmost, Key West, FL, in the lower 48 states here in the U.S. during the Spring Equinox, March 20, 2023.

As the table demonstrates it became dark 33 minutes more quickly after Sunset in Key West, FL, than it did further north in Angle Inlet, MN.

This is because Angle Inlet is further away from the equator at a higher altitude than Key West.

Location:
March 20, 2023
(Northern Most Town)
Angle Inlet, MN
(Southern Most Town)
Key West, FL
Total Time until Darkness after Sunset1 Hour
49 Minutes
1 Hour
16 Minutes
Civil Twilight7:32 pm7:38 pm
Nautical Twilight8:04 pm8:00 pm
Astronomical Twilight8:42 pm8:27 pm
True Night9:21 pm8:54 pm

The Altitude and Elevation Effect

Imagine standing at the top of a tower, high on a mountain peak overlooking a town below. Since our planet is not flat but a sphere, when the Sun rises, your visual reference to the horizon is further away compared to a person in town. You, at the top of the tower, will experience sunrise earlier and sunset later than a person from a lower location relatively nearby.

A Sun can also set at different times in close proximity relative to the perspective of a person’s view. For example, the Sun may set behind a mountain range for one viewer while another person’s view from several miles away may not be obstructed by that mountain and set for them a few minutes later.

How Seasons affect Day and Night

Due to the tilt of the Earth and its position in orbit relative to the Sun, the length of day and night changes with the seasons of the year. During summer months, there are longer days of daylight hours, with the opposite effect in winter months, seeing more darkness.
There are locations closer to the poles that experience twenty-four hours of darkness and light for a period of time, depending on the different seasons.

Midnight Sun vs. Polar Night

The Earth is tilted on its axis at 23.4º while making its journey on an elliptical orbit around our Sun.

In Summer months, this tilt is leaning towards the Sun, which in certain positions of its orbit creates days the Sun remains above the horizon, never setting within the polar circle. This is known as a Midnight Sun.

When one pole, north or south, experiences a Midnight Sun, the opposite pole experiences an entirely different effect as it is tilted away from the Sun, resulting in days of darkness in which the Sun never rises over its horizon. This is a Polar Night.

An illustration depicting Earth's position relative to the Sun during the Midnight Sun and Polar Night.
An illustration depicting Earth’s position relative to the Sun during the Midnight Sun and Polar Night.

Conclusion

So I hope this gives you a general understanding of the answer to how long after sunset does it get dark. As a result of the Earth’s tilt and position of its orbit relative to the Sun, it depends on your location and the time of year.

Here in the contiguous states of the U.S., the lower 48, it can range from:

• 1 hour and 10 minutes in the Southern States
• 1 hour and 50 minutes in the Northern States

Find Sunset and Twilight Times in Your Area

Whether you are doing a photo shoot, observing the night sky, enjoying the stars, or just looking to experience an amazing sunset, plan first by finding the times in your area so you won’t be late for the show! There are very accurate online database resources to get this information. Find the sunset and twilight times in your area right here.

A Cityastronomy logo of a cityscape under a starry night with the Cityastronomy name worded across the circular picture.
Written by Darin Anthony

Astronomy has peaked my curiosity and imagination from an early age. I am always thrilled to read about the latest galactic discovery or planning my next celestial observation. More about me [..]

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