The amount of time it takes for it to get completely dark after sunset varies depending on a few factors. Generally speaking, it takes around 30-40 minutes for it to become completely dark after the sun dips below the horizon at sunset. However, the exact timeframe can be influenced by things like location, time of year, weather conditions, and light pollution.
In the minutes and hours after sunset, the sky goes through various stages of darkness before it becomes completely black. Civil twilight, nautical twilight, and astronomical twilight are the intermediate phases between sunset and full nighttime darkness. Read on to learn more about how long after sunset it takes to get dark.
Stages of Darkness After Sunset
There are three established phases that occur in the period between sunset and complete darkness:
Civil Twilight: This is the brightest phase after sunset, lasting around 30 minutes. There is still enough natural light during civil twilight to carry out most outdoor activities without artificial lighting. The horizon remains clearly defined and visible to the naked eye.
Nautical Twilight: During nautical twilight, the brightness drops rapidly as natural light continues to fade. It is dark enough that artificial lighting is needed for most outdoor activities. Nautical twilight lasts for around 30 minutes after civil twilight. The horizon becomes less well-defined and harder to discern during this phase.
Astronomical Twilight: This is the final stage before it becomes completely dark. Astronomical twilight lasts for about 30 minutes after nautical twilight. There is very little natural light left, making the sky quite dark. Only the brightest stars are visible to the naked eye during astronomical twilight. The horizon is no longer visible or distinguishable.
After astronomical twilight ends, it is considered fully nighttime and the sky will appear at its darkest. This entire twilight sequence can last around 90 minutes or more after sunset. However, the exact durations can vary.
Factors That Influence How Quickly It Gets Dark
Several key factors determine how quickly it becomes completely dark after the sun sets each day:
Location: The closer you are to the equator, the shorter the period is between sunset and full darkness. This is because locations around the equator do not experience much seasonal variation in day length or the angle of sunlight throughout the year. Places farther north or south of the equator have longer periods of twilight after sunset, especially in the summer when days are longer.
Season: During the summer months, it takes longer to become completely dark because the days are so much longer. The opposite is true in the winter when nights are longer. In summer, there can be well over an hour of fading light after sunset before full darkness. In winter, it may take only 30 minutes.
Weather: Cloudy, stormy weather will make the sky become dark more quickly after sunset. The cloud coverage blocks sunlight from illuminating the sky. On very clear days, especially in summer, the sunset light can linger for a while before fading.
Light Pollution: In urban areas with significant artificial lighting, it takes longer for true darkness to occur after sunset. The artificial lights overwhelm the natural fading of light. Areas far from city lights and with clear dark skies will reach full darkness more quickly.
Exact Timeframes From Sunset to Darkness
While the general timeframe is around 30 minutes each for civil, nautical, and astronomical twilight, the exact durations vary significantly across different latitudes, seasons, and weather conditions. To demonstrate, here are some estimates for the time between sunset and complete darkness under different circumstances:
| Location | Season | Conditions | Time from Sunset to Full Darkness |
|---|---|---|---|
| Chicago, USA (42° N latitude) | Summer | Clear weather | 1 hour 30 minutes |
| Chicago, USA (42° N latitude) | Winter | Heavy clouds | 45 minutes |
| Key West, USA (24° N latitude) | Summer | Clear weather | 1 hour |
| Stockholm, Sweden (59° N latitude) | Summer | Clear weather | 1 hour 45 minutes |
| Singapore (1° N latitude) | Year-round | Consistently clear | 30-40 minutes |
As shown, higher latitude locations like Stockholm can take well over an hour to become fully dark in the summer, even with clear skies. More equatorial places like Singapore consistently take only 30-40 minutes year-round. The winter season also significantly shortens the time needed at higher latitudes.
Conclusion
In conclusion, the amount of time needed for the sky to become fully dark after sunset is highly variable, ranging from 30 minutes to over an hour and a half. On average under clear conditions, civil twilight, nautical twilight, and astronomical twilight each last about 30 minutes. This makes the total time around 90 minutes for it to become completely dark after the sun dips below the horizon. Location, time of year, weather, and light pollution all impact the precise duration. Observing how the sky progressively darkens through the stages of civil, nautical, and astronomical twilight can give you a better sense of how long full darkness takes to occur in your area.