The Aurora Borealis is a natural light display caused by charged particles from the sun interacting with the Earth’s atmosphere. This interaction creates shimmering curtains of green, pink, and purple light seen at high latitudes. Although the solar activity powering this phenomenon occurs year-round, viewing the aurora in summer is extremely difficult near the Arctic Circle. The primary obstacle is not a lack of solar activity, but the continuous daylight that washes out the relatively faint display.
Why Absolute Darkness is Required
The Northern Lights often appear as a faint, diffuse glow, unlike the vivid colors captured in photographs. To perceive the full range of colors and intensity, the unaided eye needs time to adapt to complete darkness. This process, known as scotopic vision, allows the eyes’ rod cells to become highly sensitive to low light levels.
Any source of light, including the moon, artificial pollution, or residual sunlight, reduces the contrast needed to see the aurora clearly. Even faint light prevents the eyes from reaching the required level of dark adaptation. The aurora must be viewed against a truly black background, especially when solar activity is not strong. Without this absolute darkness, the light show remains invisible to the observer on the ground.
The Challenge of Summer Sunlight
Summer viewing is impossible in the Arctic due to the astronomical phenomenon called the Midnight Sun or Polar Day. From roughly May through August, the Earth’s tilt prevents the sun from dipping far enough below the horizon at high latitudes. This results in continuous daylight or twilight that lasts all night long.
True night, or astronomical nighttime, is only achieved when the sun’s center is 18 degrees or more below the horizon. At latitudes above 48.5 degrees North, the sun remains too close to the horizon near the summer solstice to reach this darkness. The sky stays illuminated by scattered sunlight, preventing the necessary contrast for the faint aurora to be visible.
The solar particles still create the aurora high above the Earth, but the background sky is too bright. Even at local midnight, the sky may only reach the level of nautical or civil twilight. This persistent illumination hides the northern lights until sufficient hours of darkness return. By late August, locations in the lower Arctic begin to experience a few hours of true nighttime, allowing for the first summer sightings.
Optimal Times for Aurora Viewing
The best time to plan an aurora trip is when the nights are longest and darkest, generally between September and April. December and January provide the maximum hours of darkness, increasing the window of opportunity for a sighting.
The equinox periods, specifically late September and March, are often cited as having slightly increased geomagnetic activity. This heightened activity is due to the way the solar wind interacts with the Earth’s magnetic field, which can lead to stronger and more frequent auroral displays. Therefore, targeting a trip between late August and early October, or in March, balances the need for long, dark nights with the statistical likelihood of increased solar events. These viewing seasons offer the most favorable conditions for witnessing the Northern Lights.