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Oct 03, 2026

KP index and the Northern Lights: what it means and how we use it

Almost every guest who books a Northern Lights tour with us has an aurora app on their phone, and almost every app leads with one number: the KP index. We are asked about it every evening – “it says KP 2, is it worth going out?” – so this article explains what the number really measures, where it comes from and why, here in Lapland, it is only one piece of the puzzle.

We explain it the way our guides do on the bus: plainly, with the figures taken from the institutions that publish the data, the U.S. NOAA Space Weather Prediction Center and the Finnish Meteorological Institute (FMI).

In short: the KP index (written Kp) is a global 0–9 scale of how disturbed the Earth’s magnetic field is, calculated for three-hour periods. Higher values mean a stronger geomagnetic disturbance, and Kp 5 or more is classed as a geomagnetic storm. In Finnish Lapland, auroras are common even when Kp is low, so what decides a good night is usually local magnetic activity plus a dark, clear sky. That is why, on our Professional Guaranteed Northern Lights Hunting Tour from Rovaniemi by Bus (from 109 €, usually 4–5 hours), the guides look at the forecast, the clouds and the aurora activity together before choosing where to drive.

At a glance

• From: 109 €
• Experience type: Northern Lights tour
• Duration: Total duration of tour is usually 4-5 hours depends on conditions of the day
• Difficulty: Easy
• Book in Advance: Cut off: 1 hours before start time
• Included: Professional Northern Lights guide & photographer in English (other languages available on request: (Spanish, Catalan, Portuguese, French, Italian, German, Czech, Slovak, Polish, Ukrainian, Macedonian & Finnish. PLEASE NOTE LIMITED AVAILABILITY FOR OTHER LANGUAGES) If another language is required. Please send us an email or WhatsApp after booking.); Information about the Northern Lights; Professional DSLR photos (delivered securely online); Northern Lights guarantee, if we don’t capture Northern Lights you get 100% your money back!; Hot drinks & light snacks
• Cancellation: Free cancellation 24 hours before the activity. We will charge a cancellation fee of 100% if booking is cancelled less than 24 hours before the activity.
• Accessibility: Not wheelchair accessible; Not stroller accessible

What the KP index actually measures

The K-index describes disturbances in the horizontal component of the Earth’s magnetic field. According to NOAA’s Space Weather Prediction Center, it is an integer from 0 to 9, where 1 is calm and 5 or more indicates a geomagnetic storm. It is based on the largest fluctuations a magnetometer records during a three-hour interval.

The planetary index, Kp, is the mean standardised K-index from 13 geomagnetic observatories located between 44 and 60 degrees of northern or southern geomagnetic latitude – stations in places such as Canada, the United States, the United Kingdom, Germany and Australia.

Two things follow from this. First, Kp is a measure of disturbance in the magnetic field, not a photograph of the sky: it does not measure the auroras themselves. Second, it is a global average built from mid-latitude observatories, for three-hour blocks. It tells you how active the whole system is, not what is happening above one particular forest north of Rovaniemi at 22:15.

From Kp to storm levels: the G-scale

NOAA links the higher Kp values to its geomagnetic storm scale, which is what you see in the news when a big storm is forecast:

• Kp 5 = G1 (minor) – aurora commonly visible at high latitudes.
• Kp 6 = G2 (moderate) – aurora typically seen down to around 55° geomagnetic latitude.
• Kp 7 = G3 (strong) – typically around 50° geomagnetic latitude.
• Kp 8 to 9- = G4 (severe) – typically around 45° geomagnetic latitude.
• Kp 9 = G5 (extreme) – typically around 40° geomagnetic latitude.

Notice what this scale is designed for: it describes how far towards the equator the auroras can reach during a storm. That is exactly the question people in central Europe or the United States need answered. For us in Lapland, the question is different, because we already live under the auroral zone.

Why a low KP is not a “no” in Lapland

The Finnish Meteorological Institute puts it simply: in Lapland, auroras are quite common always, even during solar minimum. FMI estimates that in Lapland – it gives the ski resorts of Ylläs, Levi and Saariselkä as examples – auroras occur on roughly 50% of nights. It also notes that auroras occur fairly evenly throughout the year, with slightly higher rates in spring and autumn than in winter and summer. In summer, of course, the nights are too light to see them.

FMI’s description of how to read magnetic activity is the key to the whole question: geomagnetic activity is closely linked with auroras, and when the activity level exceeds a location-specific threshold, it is probable to see auroras, weather permitting. The threshold depends on where you stand. A number that means nothing for London can mean a visible display over Lapland.

So when a guest shows us an app with a low Kp and asks whether to cancel, our honest answer is: the number alone does not decide it. Clouds usually matter more.

The forecast versus the real-time picture

There are two kinds of information hiding behind the word “KP” in most apps:

• Forecasts. NOAA’s Space Weather Prediction Center issues a plain-language three-day forecast every 12 hours, at 00:30 and 12:30 UTC, covering the outlook for geomagnetic activity. Forecasts are useful for spotting a promising evening days in advance, but they are forecasts – the actual activity can come earlier, later, weaker or stronger.
• Observations. Measured magnetic activity tells you what is happening now. In Finland, FMI runs a service based on measurements from its own automatic magnetometer stations, showing geomagnetic disturbances over the past hours; FMI notes that these disturbances tell us about the probability of auroras occurring.

Remember too that Kp values are published in UTC three-hour blocks. Finland is two or three hours ahead of UTC depending on the season, so the “tonight” block in an app may not line up with the hours you are actually outside.

The sky still has the final say

No magnetic index can see through clouds. FMI’s advice for aurora watchers is to find a dark, open place, preferably far from town lights, with an open view towards the north, and it notes that the best conditions – a dark, cloudless night – are practically always cold in Finland. For the same reason, FMI names March and early April as a particularly good time in Northern Finland, when aurora frequency and the weather tend to work together.

This is why we care as much about cloud forecasts and light pollution as about any space-weather number. A modest level of activity over a clear sky far from the street lights is a far better evening than a big storm behind thick cloud.

How this shows up on our tours

On our Professional Guaranteed Northern Lights Hunting Tour from Rovaniemi by Bus, each night our guides study weather forecasts, cloud conditions and aurora activity before choosing the best possible direction for the tour. There is no fixed viewpoint: some nights the best conditions are close to Rovaniemi, other nights require a longer drive into the surrounding Arctic landscapes. The tour usually lasts 4–5 hours depending on the conditions, and the start time can vary between 17:00 and 21:00 – we confirm it by email by 14:00 on the day.

Your guide explains what is happening in the Arctic sky during the evening, so this is a good place to ask about the numbers on your app. Professional DSLR photos are included and delivered online within 2–3 business days, and the tour carries our Northern Lights guarantee: if we do not capture Northern Lights, you get 100% of your money back. Hot drinks and light snacks are included. Please bring your passport, and keep in mind two honest points from the product page: the Northern Lights look stronger on camera than to the naked eye, and aurora hunting involves a lot of driving and waiting, so it takes patience.

If you prefer a smaller group, the Professional Small Group Northern Lights Hunting Tour from Rovaniemi – Guaranteed (from 199 €) travels in groups of 2–8 with unlimited mileage and time, typically 4–10 hours, and includes winter clothing and pick-up within 10 km of the city centre.

When to choose a fixed-location tour instead

A hunting tour is built around chasing the best sky. If you would rather have a warm, relaxed evening in one place and let the auroras come if they come, our fixed-location tours are the better match: the Northern Lights Tour at the Campfire (from 99 €, 3 hours) or the Northern Lights Tour in Atmospheric Cottage (from 109 €, 3 hours). Both include pick-up within 10 km of Rovaniemi city centre, winter clothing, snacks and drinks and information about the Northern Lights – but they do not carry the aurora guarantee.

Book the guaranteed hunting tour if seeing the lights is the main goal of your trip and you are happy to spend the evening on the road. Choose the campfire or the cottage if the evening itself matters as much as the sky. You can see all our options on the Northern Lights tours page, and for the physics behind it all, read how auroras are formed and our article on solar maximum and the 2026 aurora season.

Frequently asked questions

What does KP stand for in the Northern Lights forecast?

Kp is the planetary K-index, a 0–9 measure of disturbance in the Earth’s magnetic field over a three-hour period, averaged from 13 geomagnetic observatories. NOAA classes Kp 5 or more as a geomagnetic storm.

Can you see the Northern Lights in Rovaniemi with a low KP?

Often, yes. The Finnish Meteorological Institute notes that auroras are common in Lapland even during solar minimum, and that auroras become probable when magnetic activity exceeds a threshold that depends on your location. A dark, clear sky usually matters more than the Kp number.

Is KP 5 needed to see auroras in Lapland?

No. Kp 5 marks a minor geomagnetic storm (G1) on NOAA’s scale, which is about how far south auroras can reach. Lapland is far enough north that displays are regularly seen without a storm, weather permitting.

Do your guides use the KP index?

Our guides study weather forecasts, cloud conditions and aurora activity every night before choosing the direction of the tour. The magnetic activity is one part of that decision, together with clouds and darkness.

What happens if we don’t see the Northern Lights on the guaranteed tour?

On the Professional Guaranteed Northern Lights Hunting Tour from Rovaniemi by Bus, a full 100% refund is given if we don’t capture any auroras.

How long does the guaranteed bus tour take?

The total duration is usually 4–5 hours, depending on the conditions of the day. The start time varies between 17:00 and 21:00 and is confirmed by email by 14:00.

Ready to book?

You may also like

• Professional Small Group Northern Lights Hunting Tour from Rovaniemi – Guaranteed — from 199 €, Total duration of tour is usually 4-10 hours depends on conditions of the day
• Northern Lights Tour At The Campfire — from 99 €, 3 hours
• Northern Lights Tour in Atmospheric Cottage — from 109 €, 3 hours

Sources

• NOAA Space Weather Prediction Center – Planetary K-index
• NOAA Space Weather Prediction Center – NOAA Space Weather Scales
• NOAA Space Weather Prediction Center – 3-Day Forecast
• Finnish Meteorological Institute – Auroras in Finland
• Finnish Meteorological Institute – Auroras and space weather
• FMI Space – Auroras in Finland