How Long After Sunset Does It Get Dark?

The sun sets, and then — for a while — nothing much happens. The sky stays bright, the streetlights hesitate, and if you’re timing a walk home, a drive, or a photo, you’re left guessing how long the light will hold. The guess has a real answer, and it’s more interesting than a single number.

For most of the continental United States, the working answer is: it’s functionally dark about 25 to 35 minutes after sunset, and completely dark about 70 to 100 minutes after sunset. Both figures stretch in summer, shrink toward their minimum in spring and fall, and grow steadily the farther north you live — to the point where, in parts of Alaska in June, the second one never arrives at all.

Three Different Kinds of “Dark”

The wait after sunset has stages, because the sun keeps lighting the atmosphere from below the horizon long after it disappears from view. Astronomers slice this into three twilight phases, and each one answers a different everyday question.

Civil twilight ends when the sun reaches 6° below the horizon. Until then, there’s enough natural light to walk, work, and see color; the brightest planets appear, but the sky is clearly still lit. When civil twilight ends, most people would say it is dark out — this is the “25 to 35 minutes” answer, and it’s the one that matters for getting off a trail or a jobsite without a headlamp.

Nautical twilight ends at 12° below. The horizon line disappears, and outdoor activity without artificial light stops being practical. Whatever glow remains sits low in the west.

Astronomical twilight ends at 18° below. Only now has the sun’s scattered light fully left the sky — the “70 to 100 minutes” answer. The difference from nautical darkness is invisible in a city but obvious at a dark site, and it’s the threshold that matters if you’re waiting for the Milky Way.

In between sits a photographer’s landmark: the blue hour, roughly when the sun is 4–6° down and the sky turns a deep, even blue — arriving around 15 to 25 minutes after sunset for most of the country.

Why the Wait Depends on Where You Live

The sun moves along its path at a fixed 15° per hour — that never changes. What changes is the steepness of that path relative to the horizon, and steepness is set by your latitude.

At the equator, the sun sets nearly straight down, plunging vertically toward that 6° mark. At higher latitudes the sun’s path meets the horizon at a slant, so it slides sideways as it sinks — covering the same 15° per hour along its track, but losing altitude much more slowly. The farther north you are, the shallower the slide and the longer every twilight phase lasts.

Around the equinoxes — when twilight is near its yearly minimum — the wait from sunset to the end of civil twilight looks roughly like this:

City	Latitude	Sunset to “functionally dark”
Honolulu	21°N	~25 minutes
Miami	26°N	~26 minutes
Dallas	33°N	~28 minutes
Denver	40°N	~30 minutes
Seattle	48°N	~35 minutes
Anchorage	61°N	~50 minutes

Full darkness — the end of astronomical twilight — follows the same pattern at roughly triple the duration: about 75 minutes after sunset in Miami, 85 in Denver, an hour and three quarters in Seattle in spring, and considerably more in summer everywhere.

Summer Stretches the Wait, and Not Just a Little

Season adds a second layer. Twilight runs shortest near the equinoxes, when the sun’s path crosses the horizon most steeply, and longest around the June solstice, when the path flattens out. (There’s a smaller secondary bump around the December solstice too — twilight in midwinter is slightly longer than in March or September, a detail almost nobody notices but the math insists on.)

At Miami’s latitude the seasonal difference is minor — a few minutes. At Denver’s, civil twilight grows from about 30 minutes at the equinox to nearly 40 at the June solstice. At Seattle’s, it approaches 50 minutes in late June, which is why Pacific Northwest summer evenings seem to linger forever: a 9:10 p.m. sunset with 45+ minutes of usable light after it means the sky is still glowing at 10 o’clock.

Combine late solstice sunsets with stretched twilight and the practical consequence is striking. In late June, full astronomical darkness arrives around 10:45 p.m. in Miami, after 11:30 p.m. in Denver — and in Seattle, briefly, not at all.

The Latitudes Where Night Gives Up

Each twilight phase has a hard geometric cutoff. Around the June solstice, the sun’s lowest point below the horizon is your latitude plus the Earth’s 23.4° tilt, minus 90°. Work through the arithmetic and three lines fall across the map:

• Above about 48.5°N, the sun never reaches 18° down at midsummer, so astronomical twilight never ends. Seattle, at 47.6°N, squeaks under the line and keeps a sliver of true darkness even in June; cities along the northern border spend several weeks without any.
• Above about 54.5°N — southern Alaska — even nautical twilight persists all night around the solstice. The horizon stays visible at 1 a.m.
• Above about 60.5°N, civil twilight itself never ends. Anchorage sits at 61.2°N, which means that for a stretch of June the city never gets functionally dark at all: the sun sets before midnight, skims along just below the horizon, and rises again about four hours later, with the sky bright enough to read outside the whole time. This is the “white nights” phenomenon, and it happens well south of the Arctic Circle’s midnight sun.

Winter mirrors all of this in reverse — high-latitude December days are short, but their twilights are long and gentle, padding the brief daylight with an extra hour of usable half-light on each end.

The 30-Minute Rules Written Into Law

Twilight isn’t just an astronomical curiosity; chunks of it are codified. Most US states require headlights from 30 minutes after sunset until 30 minutes before sunrise — a legislative approximation of civil twilight that dates back decades and works reasonably well across the middle latitudes (less well in Alaska, where the statute can demand headlights while the sky is still bright enough for sunglasses).

Hunting regulations lean on the same window: legal shooting light in many states runs from 30 minutes before sunrise to 30 minutes after sunset, which is why hunters check official time tables rather than the sunset line on a weather app. Aviation uses civil twilight directly — pilot logging rules and aircraft lighting requirements hinge on it. Streetlights, on the other hand, follow none of this: nearly all are switched by photocells reacting to actual sky brightness, which is why they flicker on earlier under heavy overcast than on a clear evening.

That overcast point applies to your own planning too. The twilight clock describes a clear sky; thick clouds can make it feel like the light has failed 15 minutes early, while a clear sky, an open horizon, and snow on the ground can keep the world navigable well past the official end of civil twilight.

Morning Runs the Same Tape Backwards

Everything above applies symmetrically before sunrise. First light — the start of morning civil twilight — arrives that same 25 to 35 minutes before the sun does, and the sky begins brightening from full darkness about an hour and a half before sunrise. If you’re timing a headlamp start for a summit sunrise, those are the numbers that matter, not the sunrise time itself.

The minute-by-minute schedule for any given evening — sunset, each twilight boundary, and how they drift through the year — depends on your coordinates. Each city page computes the sequence for representative city-center coordinates, tonight and for any month ahead. Use it as a planning baseline and leave a safety margin for terrain, weather, and your actual position.