Aurora questions, answered honestly
The general questions every northern-lights trip raises. For questions about a specific place — thresholds, seasons, where to stand — each destination page has its own section.
What Kp index do I need to see the northern lights?
It depends entirely on where you stand. Yellowknife sits almost under the auroral oval and often needs only Kp 0-1; Tromsø typically needs Kp 1; Reykjavík more like Kp 2. That is why this site scores each destination against its own threshold instead of quoting one global number — a "low" Kp night can still be a great night in the right place.
What actually ruins most aurora trips?
Clouds — not quiet solar activity. A strong display above an overcast sky is worth nothing, which is why the score here multiplies cloud cover into the verdict and names it plainly when it is the problem. If you remember one thing: plan around the cloud forecast, chase gaps, and give yourself several nights.
What time of night is best?
Activity statistically peaks in the hours around local magnetic midnight — roughly 21:00 to 02:00 at most destinations — but substorms can fire earlier or later. Each destination page breaks tonight into 3-hour blocks so you can see which window looks strongest instead of standing outside all night.
Can I see the aurora when the moon is full?
Yes. A bright moon washes out faint detail and shortens how far you can see into weaker displays, but it never blocks a strong one — plenty of iconic photos were shot under moonlight, which also illuminates the landscape. The score dims by at most a quarter for a full moon above the horizon.
Will my phone camera capture it?
Modern phones do surprisingly well: night mode, 3-10 second exposure, lens propped steady or on a small tripod. The camera gathers more light than your eye, so it will often show green where you see grey — useful as a detector on marginal nights. For moving curtains, shorter exposures keep the structure.
How far ahead can aurora be forecast honestly?
Detailed Kp forecasts are good for about three days — the time solar wind takes to arrive after the sun shows its hand. Beyond that, the 27-day outlook only reflects the sun’s rotation and is a tendency, not a promise; this site labels those nights "rough estimate" rather than pretending. No one on Earth can predict individual substorms hours ahead.
Is this a good year to go?
Yes — the current solar cycle peaked recently and the declining phase that follows historically produces some of the strongest storms, with elevated activity typically lasting a few years past maximum. Within any year, the weeks around the equinoxes (March and September) run geomagnetically hottest; the records behind our monthly odds show it clearly.
Do I need a guided tour?
Not for the aurora itself — a dark spot and patience work. Where guides earn their money is cloud-dodging: on marginal nights they drive toward whatever gap the forecast shows, sometimes hours inland, and they know the dark spots and the roads in winter. If the sky is forecast clear, save the money; if it is patchy, a chase beats standing still.
Why is the aurora green — and sometimes red or purple?
Colors come from which gas gets hit and at what altitude. Oxygen around 100-300 km glows the dominant green; the same oxygen much higher produces deep red during strong storms; nitrogen lower down adds purple-pink fringes to active displays. Cameras exaggerate all of it — expect the eye to see softer colors than the photos.
How are the scores on this site calculated?
Four factors multiplied together — darkness, geomagnetic activity versus the local threshold, cloud cover, and moonlight — per 3-hour block of the night, using NOAA, GFZ Potsdam and Open-Meteo data. No machine learning, no hidden weights; the full formula is on the methodology page, because a forecast you cannot inspect is just vibes.