Where and when to see the northern lights without wasting a week
The Kp index alone can't tell you whether to go outside. Here are the four conditions needed to see the northern lights, and the season with the best odds.
Weather
Norya
Norya: the northern lights app that answers instead of displaying
Norya is the northern lights app that answers one question: can I see an aurora, here, tonight. One score from 0 to 100, and the window to go out in.
Free iOS 18+ Coming soon
Get notified at launch
The free tier genuinely lets you see an aurora. Norya Pro adds alerts and a 72 hour horizon, as a 15 day pass at €2.99, monthly at €3.99 or yearly at €24.99.
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0 to 100
one score, not a Kp index to interpret yourself
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−10°
the darkness threshold used, a month of season gained
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250 tests
139 of them on the scoring engine alone
01 Where it started
You asked about an umbrella, they gave you the barometer
Most aurora apps show the Kp, a planetary index computed over three hours, and leave you to draw your own conclusions. That is exactly like answering with atmospheric pressure when somebody asks whether they need an umbrella.
Kp knows nothing about your sky. Kp 7 under solid stratus gives you nothing, and a quiet night with the Moon down and clear air can absolutely deliver. The data is true, it simply is not the answer.
Norya answers for you. One number, one sentence, one time, and everything behind it so you can check the number is telling the truth.
A score, a verdict, a window. The rest is available, it is just no longer required reading.
02 The score
A northern lights app that makes the call for you
The score runs from 0 to 100 for your position and the hour ahead. It combines five things: auroral activity from NOAA's OVATION model, the three cloud layers above you, real darkness from the Sun's position, the Moon's phase and altitude, and the solar wind averaged over thirty minutes.
It is never presented as a percentage chance. Announcing a 79 percent probability would imply a calibration that does not exist yet, and I would rather have a number that is honest about what it is than one that flatters what it is not.
During the day the current score would be zero no matter what, because the Sun alone cancels it. The screen then shows the peak of the coming night and says so, because that is the question you actually ask at two in the afternoon.
03 The timing
Knowing when to go out, not just whether it is worth it
An aurora does not last all night. Norya works out the best observation window, its length and its countdown, then gives the score for every hour until morning.
The times shown are always those of the place you are looking at, never those of your phone. When you plan a Tromsø night from Paris, that difference stops you setting an alarm for nothing.
04 The map
The auroral oval, live, above your head
The auroral oval is drawn on the globe in real time, with the day and night terminator as two lines: gold at sunset, blue at the entry into full darkness.
Tapping a point queries it and returns its name, its zenith probability and its score. It is the most direct way to understand why northern Norway works and why your own garden, tonight, will not.
05 The places
Five destinations compared at a glance
Tromsø, Abisko, Rovaniemi, Reykjavik, Murmansk. Each with the local time there, the sky it has and its current score.
This is the screen for somebody planning a trip and still hesitating between two countries, or following somebody else's night. Tapping a card makes it the one you follow on the home screen.
06 The detail
Everything behind the number stays available
Answering for the user does not mean hiding the data. The hourly cards give the forecast sky, the cloud cover, the score and the temperature. Below them, three curves you can scrub through and the full set of measurements.
Kp, Hp30, Bz, Bt, solar wind speed and density: it is all there, and it is all free. It just is not a prerequisite for making up your mind any more.
07 The alerts
Being told when the sky opens, without thinking about it
Norya watches your location even with the app closed and tells you when the conditions line up. The threshold is adjustable, so is the confidence requirement, and quiet hours prevent the four in the morning notification on a Tuesday.
The service sending those alerts runs on a Cloudflare Worker, and it applies the same engine as the app, factor for factor. A widget announcing 00 while the app shows 74 would be a bug, and it is treated as one.
What it does
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A score from 0 to 100
For your position and the hour ahead, with a two line verdict and the ideal window.
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Sky, Moon and Sun included
Three cloud layers, visibility, Moon phase and altitude, real twilights for the place you are looking at.
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The live auroral oval
On the globe, with the day and night terminator and your pinned places, queryable on tap.
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The raw measurements, free
Kp, Hp30, Bz, Bt, solar wind speed and density, plus the three day NOAA forecast.
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Alerts with the app closed
Threshold, confidence requirement and quiet hours, each adjustable on its own.
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The maths runs on your iPhone
The score depends on no server. Offline, the app shows the last calculation and says so.
The threshold that adds a month to the season
Most aurora apps wait for astronomical night, when the Sun has dropped eighteen degrees below the horizon. That is the official definition of darkness, and it is too strict for this particular use.
Sky brightness measurements tell a different story. Between eighteen and twelve degrees below the horizon, the background sky varies by a factor of seven. Between twelve and six degrees, it varies by a factor of four hundred. In other words, most of the night is already won well before the official threshold.
So Norya puts its observability limit around ten degrees. In practice the Tromsø season opens in late August instead of 20 September, and closes correspondingly later in spring. A month gained at each end, simply by reading the measurements rather than copying a convention.
What it refuses to do
These rules live in the code, not in a statement of intent.
When weather data is unavailable there is no score. Not zero, not a neutral value: the app says it does not know. When the sky is overcast the score is zero, with no floor letting sixty percent of the total through under solid stratus. And two sources are never maximised together: when OVATION and the Kp fallback disagree, it is the displayed confidence that drops, not the score that climbs.
These refusals apply to the score, never to the data. The weather detail stays available at any time: hour by hour cloud cover, visibility, temperatures, the position of the Sun and the Moon. If you want to check why a score is low, or make up your own mind against the app’s verdict, it is all there and it is all free.
That is rare in this category, where a wrong number is generally preferred to an admission. I prefer the opposite, because an app that sends you out for nothing twice in a row never gets opened again.
What comes next
Calibrating the score against real observations is the work that matters. Until that exists, the score stays a score and will not present itself as a probability.
If you are chasing the lights this winter and want to test the app in the field, write to me. A well documented failed night teaches me more than ten successful ones.
Privacy and terms
Norya has no account, no tracker and not the slightest bit of analytics. What stays on the iPhone, what goes to the alert server if you turn alerts on, and how to erase all of it are set out in the Norya privacy policy. The rules of the service, the scientific sources and their licences, what is free and what Pro adds are in the terms of use and legal notice.
Frequently asked questions
How does a northern lights app like Norya work?
It combines auroral activity from NOAA's OVATION model, the cloud cover above you, real darkness from the Sun's position, the Moon, and the solar wind. The result is a score from 0 to 100 for your position and the hour ahead, along with the best observation window.
Why not simply look at the Kp index?
Kp is a planetary index computed over three hours. It knows nothing about your clouds, your Moon or your latitude. A high Kp under a solid overcast gives you nothing, and Norya shows zero in that case rather than an encouraging number.
What happens when the weather data is unavailable?
The app gives no score and says so. It does not show zero, because zero would mean no chance at all, which is not the same thing as I do not have the data.
Do I need an account?
No. No sign-up, no password, no name. The alert service only ever receives an anonymous token, a coordinate and your thresholds, and one button erases everything, server side included.
What is free and what does Pro add?
Free gives you the score, the verdict, the ideal window, twenty-four hours of forecasts, the map, every scientific measurement and as many saved places as you want. Pro adds alerts, a 72 hour horizon, the map timeline, detailed solar wind and the long term trend.
How much does Norya Pro cost?
Three options. A 15 day pass at €2.99 that stops on its own and is not a subscription, a monthly plan at €3.99, or a yearly one at €24.99.
Which version of iOS do I need?
Norya requires iOS 18 or later.
Coming soon
Norya is coming very soon.