Seeing the northern lights is never guaranteed — it is the product of multiple atmospheric, solar, and geographic conditions aligning at the same time. Understanding what drives aurora activity and visibility is the single most important thing you can do to improve your chances. Below are the key factors, ranked in order of importance. Some of these you can plan around, others you simply monitor and react to — but all of them matter.
Cloud Cover
This is a make or break, and therefore the most important (along with #2 on the list). If there is a thick low/mid level cloud cover chances of seeing anything (no matter how active solar conditions are) would be near zero. The aurora cannot penetrate through thick clouds. Now, like everything in life, there are caveats. If it is ‘cloudy’ , but the clouds are high/thin ‘cirrus’ clouds, viewing the aurora is still possible (although not ideal). And if the forecast is for partly or mostly cloudy skies, any clear patches can provide windows, and sometimes the most dramatic/unique photographs of the aurora have some clouds present.
Nighttime / Darkness
This one is obvious and also a ‘make or break’ factor. Daylight or bright twilight means no auroras. You need darkness or ‘darker’ forms of twilight for the aurora to appear. You can monitor night, day, and twilight times for specific locations on many websites, which can be very different than your home times. Therefore planning here is essential. I get into much greater detail on specific twilight types and photography/viewing suited to each in my PDF guide and book.
Geographic Location (Magnetic Latitude)
The further north, the better (for the most part). This is a very important factor, and for more detailed information see the ‘What are the best locations to see them’ page on this website.
Geomagnetic Activity (Kp Index)
Now we start getting more nuanced and ‘into the weeds’. For instance, if you are in a prime auroral oval location, it is completely dark, and there is a clear sky (#1 – #3 on this list are in your favor) on most nights you will some aurora activity. From this point down the list, it is just a question of how impressive the show will be. This factor, representing overall geomagnetic activity largely determines the potential of the aurora that night. Please refer to the KP index graph at the bottom of this page for more detailed information on this metric. A KP of 0 could indicate very weak or no aurora in Iceland, where a KP of 9 can create a great show as far south as southern California, Arizona, Texas, and the Carolinas in the USA.
Bz Magnetic Orientation
In short, this metric (paired with the KP index) is where the ‘money is made’. The Bz metric measures how well the space magnetic field lines up with the Earth’s. If they line up (N/S; opposites like a magnet) they ‘click’ and solar particles and wind (what causes aurora) enter the upper atmosphere and cause high activity shows. If there is a (N/N) alignment, much more quiet and subdued conditions are likely. So, everything else equal you want to see a Bz strongly south/negative, and the more south/negative the better. At 40N – 41N (where I am located) I have seen KP8/9 with a -50Bz (extreme) and the show/colors/intensity were incredible. Months later, an arguably stronger disturbance of KP9 occurred, but paired with a strongly positive Bz, all that was visible was a faint/weak hint of color on the northern horizon through photographs.
Light Pollution / Artificial Light
All the factors above you can attempt to forecast/plan around, but cannot change. You do have direct control over your specific chase location and light pollution (artificial light caused by city/town glows at night). This can mute out the aurora (especially more modest displays). No matter how strong the aurora, you will not be able to see it in Times Square, NYC. However, just 40 miles west away from city lights, a relatively modest display can be seen. Within the ‘helpful websites/apps’ section of this site I show you some very useful tools/maps that help you plan a chase around minimizing the light pollution problem.
Solar Wind Conditions
Solar winds, a measure of how fast solar particles are bombarding the Earth, can have an important (although usually secondary) impact on how vivid the aurora displays will be. The faster the solar the wind, the better. Average speeds are between 300 – 400 kilometers/second. Once speeds exceed 500, and especially 600+, auroras can get very active (especially in terms of movement (dancing, pulsating, morphing into different shapes, etc.). Coronal holes on the sun (where fast solar winds escape the sun and head our way) are one of the more predictable forms of higher aurora activity. To some extent, these events can be forecast as much as 27 days in advance.
Earth Wind Conditions
Although earth wind conditions have no impact on the activity level or viewing conditions of the aurora, they can cause problems in terms of cold/wind chills, photography (tripod steadiness/blurry photos), and general safety/travel/flight cancellations. Keep an eye on this one (especially in Iceland, southern Alaska, and coastal Norway)…it can be a gamechanger despite being last on the list. Anything above 30mph-35mph winds can cause large complications for a chase (especially in terms of photography).
Kp Index Reference Guide
| Kp Value | Aurora Activity Level | Average Frequency | Conditions / Viewing | Approx. Latitude Visible | Likely Cause |
|---|---|---|---|---|---|
| 0 | Quiet | Not applicable | faint, diffuse, or absent aurora even at high latitudes | 65N+ | very low solar activity |
| 1 | Quiet | Roughly 90% of time equal or greater | faint, diffuse or stable ‘arc’ formations | 61N – 64N+ | low solar activity |
| 2 | Unsettled | Roughly 70% of time equal or greater | noticeable lights, stable/moving ‘arc’, other formations possible | 57N – 61N+ | low/average solar activity |
| 3 | Unsettled | Roughly 50% of time equal or greater | noticeable lights, moving arc(s), other formations likely, long lasting | 54N – 57N+ | normal solar activity |
| 4 | Active | Roughly 30% of time equal or greater | active arc(s), other formations, some other colors, brief coronas likely | 51N – 54N+ | normal or slightly above normal solar winds/disturbance |
| 5 | Minor Storm (G1) | Roughly 5% – 10% of time equal or greater | multiple and simultaneous formations likely, several colors, coronas likely, fast movement | 47N – 51N+ | Weak CME or strong solar winds/coronal hole |
| 6 | Moderate Storm (G2) | Roughly 3% – 6% of time equal or greater | many colors and formations, rapid movement, long lasting coronas, memorable show | 41N – 45N+ | Moderate CME/strong solar winds/coronal hole |
| 7 | Strong Storm (G3) | Roughly 1% – 3% of time equal or greater | Memorable show in all aspects; many never see this level of activity in person | 37N – 41N+ | Moderate – Strong CME/Extreme solar winds/strong coronal hole |
| 8 | Severe Storm (G4) | less than 1% of time equal or greater | Spectacular and awe-inspiring show; most chasers do not experience in person | 33N – 37N+ | ‘X-Flare’ CME |
| 9 | Extreme Storm (G5) | less than 0.1% of time equal or greater | Once in a lifetime show (if that) for most chasers; awe-Inspiring/intense experience | 30N – 33N+ | High end ‘X-Flare’ CME |
