What the Kp index means
The Kp index measures how strongly the Earth’s magnetic field is disturbed by the solar wind, on a scale from 0 to 9. The higher the Kp, the further south the aurora reaches.
At Kp 0 to 2 the aurora stays over the far north of Europe. From Kp 5 on, NOAA speaks of a geomagnetic storm, and the aurora can then be seen much further south than usual.
The Kp only tells you whether the aurora can reach your latitude. You also need a dark night and a clear sky, so check the cloud forecast as well.
| Kp | Activity | Possible in (examples) |
|---|---|---|
| 0–2 | low activity |  Trondheim  Oulu  Reykjavík  Umeå |
| 3–4 | moderate activity | Stockholm Oslo Helsinki  Glasgow  Hjørring  Letterkenny |
| 5–6 | geomagnetic storm | London  Hamburg  Amsterdam København Dublin  Rīga |
| 7–9 | strong geomagnetic storm | Berlin  Paris  Warszawa  Praha  Bruxelles Rotterdam |
How to improve your chances
- Go away from town lights to a place with a clear view to the north.
- Watch the sky from late evening until after midnight, when the aurora is usually strongest.
- Give your eyes 15 to 20 minutes to adjust to the dark; a phone camera often shows more colour than the eye.
- A bright moon and haze weaken the view; a clear, moonless night is best.
Data source: Space Weather Prediction Center of the US agency NOAA.