The Aurora Borealis, or Northern Lights, is often associated with cold, dark winter months. Many travelers wonder if the phenomenon ceases during summer. Scientifically, the Northern Lights are continuous, powered by the Sun’s activity year-round. They are constantly active near the polar regions, but visibility is completely obstructed by the long hours of summer daylight.
The Constant Cause: Solar Activity
The mechanism creating the Northern Lights is a constant, year-round interaction between the Sun and Earth. The Sun continuously emits the solar wind, a stream of charged particles (electrons and protons). When the solar wind reaches Earth, most particles are deflected by the planet’s protective magnetic field, the magnetosphere.
Some particles are funneled along the magnetic field lines toward the North and South Poles. They enter the upper atmosphere, typically 60 to 250 miles above the surface, and collide with gases like oxygen and nitrogen. These collisions excite the gas atoms, causing them to release energy as light. This light show is concentrated around the poles in the auroral oval. Because the solar wind is ongoing, auroral activity in the upper atmosphere is also continuous.
The Obstacle: The Midnight Sun Effect
The lights are virtually impossible to see during the summer due to the Midnight Sun. This phenomenon occurs in high-latitude regions, primarily above the Arctic Circle, because of Earth’s axial tilt. During summer, the Northern Hemisphere tilts toward the Sun, causing the Sun to remain above the horizon for 24 hours a day for extended periods.
Even in locations slightly south of the Arctic Circle, the sky never achieves the deep darkness required for auroral visibility. While the Sun may dip below the horizon, the period of twilight is so extended that the sky remains bright with persistent ambient light. The human eye perceives the aurora as a relatively faint glow, especially when compared to the brightness of daylight.
Trying to spot the aurora in a sunlit summer sky is comparable to seeing stars at noon. The subtle green, red, and purple hues are washed out by the overwhelming brightness of the atmosphere. Even if a strong auroral storm occurs in July, the resulting light is rendered invisible due to the lack of darkness. The obstruction is not a lack of aurora activity, but an excess of sunlight.
Optimal Timing for Aurora Viewing
To maximize the chance of seeing the Northern Lights, travelers should plan their trips around the period known as the Aurora Season. This window generally extends from late August to mid-April, when the polar regions experience sufficient hours of darkness. The longest and darkest nights occur between November and February, offering the most opportunity for viewing.
Statistically, the periods around the autumn and spring equinoxes, typically late September and March, often see increased geomagnetic activity due to the Earth’s orientation relative to the solar wind. The darkest hours provide the best contrast for the human eye. The peak viewing hours are usually centered around local midnight, most frequently between 10 PM and 3 AM.
Successful aurora viewing also requires monitoring space weather forecasts, particularly the Kp index, which measures the intensity of geomagnetic activity on a scale from 0 to 9. A higher Kp number indicates a greater likelihood that the auroral oval will expand southward, making the lights visible farther away from the pole. Clear skies and being away from artificial light pollution are also necessary, as clouds and city lights can easily obscure the delicate display.