The KP index is a system of measuring aurora strength. It goes from 0 to 9 (0 being very weak, 9 being a major geomagnetic storm with strong auroras visible).
So when you’re looking at the aurora forecast page, you want to look for high Kp numbers. The higher the better. Anything above (and including). Kp5 is classed as a geomagnetic storm.
To better understand the KP value and how it impacts visibility from your location you need to know your magnetic latitude. When you know the magnetic latitude you can use the table as a reference and determine if the northern lights are visible from your location or not.
|MAGNETIC LATITUDE||KP NUMBER|
It’s important to mention that a high KP value does not guarantee that the aurora is visible, however it is a great pointer to when it’s worth going out looking for it.