Tonight’s the big night when the Northern Lights are supposed to be visible throughout the United States. What exactly will be seen? We won’t know until showtime but we’ve put together a handy-dandy guide so you can appreciate the celestial lightshow.

The northern lights don’t randomly splash color across the night sky like some cosmic Jackson Pollock. Every hue is deliberate—a chemical signature revealing which atmospheric gases are being lit up, at what altitude, and with how much solar fury.

Picture Earth’s upper atmosphere as a vertical neon billboard, stacked in layers. Different “tubes” ignite at different heights depending on the energy of electrons riding down Earth’s magnetic field lines during a solar storm. The result? A color-coded map of invisible chemistry suddenly made visible.

Green: The Crowd Favorite

That luminous emerald curtain rippling overhead? Atomic oxygen, 60 to 100 miles up, getting slammed by energetic electrons. The collision excites oxygen atoms into emitting light at a very specific wavelength—one that happens to fall right in the sweet spot where human eyes are most sensitive. That’s why green dominates auroral displays, even when other colors are technically present. On an active night, those velvety ribbons sweeping the horizon are oxygen’s mid-altitude layer doing its thing.

Red: The High-Altitude Phantom

Climb above 200 miles and oxygen can also glow crimson—but only if conditions are right. At those rarefied heights, the air is so thin that excited oxygen atoms have time to radiate their slow, lazy red emission before bumping into another molecule. Drop lower where the atmosphere thickens, and frequent collisions quench that red glow before it can escape.

That’s why deep red auroras are rare showstoppers. You’ll see them capping the tops of tall auroral structures or spreading as diffuse veils during the most intense geomagnetic storms. When the entire sky bleeds red, you’re witnessing something powerful—a sign that energetic particles are hammering the uppermost reaches of our atmosphere.

Blue and Purple: Nitrogen’s Electric Edge

Now drop lower, into denser air where molecular nitrogen (N₂) and its ionized form (N₂⁺) dominate. These molecules produce brilliant blues and purples when struck by high-energy electrons—and they do it fast. The emissions are “prompt,” flashing and fading in moments, which is why you often see them outlining the racing lower edges of auroral curtains as bright indigo or violet fringes.

The physics behind this is telling: nitrogen emissions become prominent when more energetic electrons punch deeper into the atmosphere during active storms. Translation? If you’re seeing electric blue or purple at the base of an aurora, the Sun just threw a harder punch.

Mix and Match: The In-Between Zones

Auroras rarely stick to a single color. Pinks appear where green oxygen blends with red oxygen or mixes with nitrogen’s purples. Oranges flicker in the thin altitude band between red and green oxygen layers. Whites emerge when multiple wavelengths overlap—or when your eyes, working at their low-light limits, simply can’t resolve the individual hues anymore.

Here’s where photography complicates things. Long-exposure shots—especially from phones—integrate light over time, pulling faint reds and purples out of darkness that your night-adapted eyes barely registered. Your camera is essentially collecting photons your eyes sampled and discarded. That viral aurora photo showing vivid magenta? Probably real, but also probably more saturated than what anyone saw with naked eyes.

Storm Strength Rewrites the Palette

The intensity of a geomagnetic storm doesn’t just make auroras brighter—it changes their color profile through fundamental physics. Stronger disturbances accelerate electrons to higher energies, allowing them to penetrate deeper into the atmosphere where nitrogen reigns. That’s when the base of an aurora can turn electric blue or purple and move with startling speed, while higher layers glow steady green and, occasionally, blood red.

During the most energetic events, observers far south of the aurora zone may report broad red arcs without clear structure. Those are high-altitude oxygen emissions being enhanced by intense geomagnetic activity—often more visible to cameras than to the human eye, which isn’t particularly sensitive to deep red in low-light conditions.

Field Guide for Tonight

If you’re chasing auroras this evening, here’s what to look for:

Mostly green? Classic oxygen emission at 60–100 miles. Standard-issue aurora during moderate activity.

Green with violet fringes at the bottom? Energetic event. High-energy electrons are pushing into nitrogen-rich lower altitudes. Things are getting interesting.

Expansive deep red veils or red tops? High-altitude oxygen lit during a strong storm. Your camera will likely see this better than you do—but if you’re seeing it with naked eyes, the storm is significant.

Pink or magenta bands? Overlapping emissions—oxygen’s green and red mixing with nitrogen’s blues. You’re watching multiple altitude layers light up simultaneously.

Two Important Caveats

First, aurora colors can vary wildly across the sky at the same moment. Why? Because altitudes vary along magnetic field lines, and the energy of precipitating particles changes in both time and space. What looks green to the north might glow red overhead and purple to the south—all at once.

Second, local conditions matter more than most aurora guides admit. Thin clouds scatter and desaturate colors. City lights and camera white balance can shift tones toward yellow or magenta. Light pollution doesn’t just dim auroras—it can actually change their apparent color by washing out fainter wavelengths.

None of this changes the fundamental story: aurora color is altitude made visible. It’s a real-time map showing where in the upper atmosphere solar storm energy is being deposited—and which atoms and molecules are responding by singing back in light.

If tonight’s forecast delivers, don’t just stare at the brightest patch of sky. Scan vertically. That crimson cap, emerald mid-layer, and violet hemline aren’t just pretty—they’re diagnostic. Together, they tell you how powerful the storm is, how deep into our atmosphere the Sun has reached, and what kind of chemistry is happening 60 to 200 miles over your head.

The aurora isn’t decoration. It’s a readout—nature’s way of making invisible forces visible, rendering the violence of space weather as ethereal beauty.

IMAGE CREDIT: Tobias Bjørkli