What Kp do you need to see the northern lights?
It depends on how far you live from the magnetic pole. As rough planning values from our model: inside the auroral zone (Fairbanks, Yellowknife, Tromsø, Reykjavik) a Kp of 1 or 2 can put aurora overhead. Around Calgary, Edmonton and Scotland, expect roughly Kp 4 or 5 overhead, or Kp 2 or 3 for a glow on the northern horizon. For the northern US, southern Canada and much of England and central Europe, plan on about Kp 5 to 7 for aurora low on the horizon. These are guides, not minimums: displays are sometimes seen at lower Kp, and a high Kp does not guarantee one.
- What Kp measures
- Why it depends on where you live
- Kp needed for major cities
- Overhead vs on the horizon
- Beyond Kp
- Find your own number
What the Kp index measures
The Kp index is a scale from 0 to 9 that describes how disturbed Earth’s magnetic field is. Each value is derived from standardized K indices at 13 geomagnetic observatories and covers a three-hour period, so it is a global measure, not a reading of the aurora over your house. Kp 0 to 2 is quiet, Kp 3 and 4 are unsettled to active, and Kp 5 or higher counts as a geomagnetic storm. NOAA turns that into its G-scale: Kp 5 is G1 (minor), Kp 6 is G2, Kp 7 is G3, Kp 8 (including 9-) is G4, and Kp 9 is G5 (extreme).
Why the Kp you need depends on where you live
Aurora forms in a ring around each magnetic pole called the auroral oval. When Kp rises, the oval swells and its edge moves toward the equator. How far you are from the oval is set by your geomagnetic latitude, which describes your position relative to Earth’s magnetic poles rather than the geographic equator. Geomagnetic latitude is measured in a coordinate system built on Earth’s magnetic field, and the magnetic pole is not at the geographic pole, so two cities at the same ordinary latitude can need different Kp values.
A commonly used rule of thumb puts the equatorward edge of the oval at about 66.5 degrees of geomagnetic latitude at Kp 0, moving roughly 2 degrees closer to the equator for each Kp step. It is a statistical average, not a fixed boundary: the oval changes shape through the night and from storm to storm. The same idea applies around the South Pole.
Kp needed for major cities
The tables below give model estimates, not observed minimums or forecasts. For each city, aurora low on the horizon is the Kp at which you might expect a glow near the northern horizon (southern horizon in the southern hemisphere), and aurora overhead is the Kp at which the oval’s edge is estimated to reach your sky. Both use the same estimate as the northern lights forecast.
1. We approximate each city’s geomagnetic latitude with a simple tilted-dipole model of Earth’s field, with the magnetic pole near 80.7°N, 72.7°W. This is an approximation, not a full magnetic-field model, so the latitudes can be off by a degree or two.
2. We estimate the Kp at which the oval’s edge reaches the city as (66.5 minus the geomagnetic latitude) divided by 2.03, rounded up. That is the “overhead” column.
3. For the “horizon” column we subtract two Kp steps, about 4 degrees or 450 km of latitude. That gap is an assumption about how far away aurora can be seen low on the horizon, not a measured law.
Example: Calgary’s geomagnetic latitude is about 57.5°, so (66.5 − 57.5) ÷ 2.03 is about 4.4, which rounds up to Kp 5 overhead and Kp 3 on the horizon.
| City | Approx. geomagnetic latitude | Kp for aurora low on the horizon | Kp for aurora overhead |
|---|---|---|---|
| Fairbanks, Alaska | 65.6° N | 1 | 1 |
| Yellowknife, Canada | 68.6° N | 1 | 1 |
| Anchorage, Alaska | 61.9° N | 1 | 3 |
| Edmonton, Canada | 60.1° N | 2 | 4 |
| Calgary, Canada | 57.5° N | 3 | 5 |
| Winnipeg, Canada | 58.2° N | 3 | 5 |
| Vancouver, Canada | 54.6° N | 4 | 6 |
| Montreal, Canada | 54.8° N | 4 | 6 |
| Toronto, Canada | 52.9° N | 5 | 7 |
| Seattle, USA | 53.1° N | 5 | 7 |
| Minneapolis, USA | 53.6° N | 5 | 7 |
| Chicago, USA | 50.8° N | 6 | 8 |
| Boston, USA | 51.7° N | 6 | 8 |
| New York, USA | 50.0° N | 7 | 9 |
| Denver, USA | 47.4° N | 8 | Beyond 9 |
| City | Approx. geomagnetic latitude | Kp for aurora low on the horizon | Kp for aurora overhead |
|---|---|---|---|
| Tromsø, Norway | 67.5° N | 1 | 1 |
| Reykjavik, Iceland | 68.9° N | 1 | 1 |
| Rovaniemi, Finland | 63.6° N | 1 | 2 |
| Inverness, Scotland | 59.8° N | 2 | 4 |
| Oslo, Norway | 59.7° N | 2 | 4 |
| Edinburgh, Scotland | 58.1° N | 3 | 5 |
| Stockholm, Sweden | 58.0° N | 3 | 5 |
| Helsinki, Finland | 57.7° N | 3 | 5 |
| Dublin, Ireland | 56.1° N | 4 | 6 |
| London, England | 53.4° N | 5 | 7 |
| Berlin, Germany | 52.2° N | 6 | 8 |
| Paris, France | 50.4° N | 6 | 8 |
| City | Approx. geomagnetic latitude | Kp for aurora low on the horizon | Kp for aurora overhead |
|---|---|---|---|
| Hobart, Australia | 49.7° S | 7 | 9 |
| Dunedin, New Zealand | 49.4° S | 7 | 9 |
| Christchurch, New Zealand | 46.8° S | 8 | Beyond 9 |
They are model estimates, and the real answer varies from storm to storm, so treat each as a planning value that could easily be off by a Kp step or more. NOAA’s examples describe where aurora has been seen, not the Kp at which you should expect it. For instance, aurora has been documented as far south as New York during G2 (Kp 6) storms, a step below this table’s horizon figure for New York, so the table is not a firm minimum.
“Beyond 9” means the simplified model puts the oval out of reach even at Kp 9, not that aurora there is impossible. The southern hemisphere figures are the roughest, and observers in Tasmania and southern New Zealand report aurora in moderate storms, often at lower Kp than this model suggests.
Aurora overhead versus aurora on the horizon
Aurora forms 100 kilometres or more above the ground, so it can be seen from hundreds of kilometres away. Our horizon column assumes that is about two Kp steps (roughly 450 km) short of the oval, which is a rule of thumb rather than a measured limit. From a city south of the oval you usually see a green glow low in the north, with rays and curtains reaching upward in stronger displays. Aurora directly overhead needs the oval itself to move over you, which takes a bigger storm.
That is why a moderate storm can produce good photos from places that would never see aurora overhead. A clear, dark poleward horizon can improve your chances substantially, even though activity and brightness still matter.
Why Kp alone is not enough
Reaching your Kp does not guarantee a display. The same Kp can look very different depending on storm structure, local time, auroral brightness, cloud and where you stand. Check these as well:
- Bz and solar wind speed. A sustained southward Bz and a fast solar wind generally let more energy into Earth’s magnetic field. They are important short-term indicators that activity may rise, though no single reading guarantees a display.
- Cloud cover. Cloud hides the aurora completely, so a clear sky at a lower Kp beats a cloudy night at a higher one.
- Darkness and the Moon. A dark sky greatly improves what you can see, and a bright Moon washes out faint displays, although strong aurora can still show in twilight or moonlight.
- Timing. Kp is averaged over three hours, and aurora can flare and fade within that block. Activity often peaks within a couple of hours of local midnight, though strong displays can occur at other times.
- Your horizon. Light pollution, hills and buildings on the poleward side all reduce what you can see.
How to find the Kp you need for your own city
The quickest way is to enter your city in the northern lights forecast. It shows an estimate of the Kp your city needs and compares it with tonight’s conditions. For the next few nights, use the 3-day northern lights forecast, which checks the Kp forecast against cloud cover and darkness.
If Kp is below your number, don’t give up automatically. Displays are sometimes seen at lower Kp than the tables suggest, especially from a dark site with a clear poleward horizon. For a direct look at where the aurora is right now, check NOAA’s 30-minute aurora forecast.
Key takeaways
- The farther you live from the magnetic pole, the higher the Kp you need.
- In our model, aurora on the horizon needs about two Kp steps less than aurora overhead.
- The city numbers are model estimates, not guaranteed minimums.
- Kp 5 (G1) is the first storm level, and it can bring aurora to the northern US and southern Canada low on the horizon.
- Cloud, darkness and Bz decide whether a good Kp turns into a good night.
Sources and further reading
What Kp do you need to see the northern lights?
It depends on how far you live from the magnetic pole. As rough planning values from our model: inside the auroral zone (Fairbanks, Yellowknife, Tromsø, Reykjavik) a Kp of 1 or 2 can put aurora overhead. Around Calgary, Edmonton and Scotland, expect roughly Kp 4 or 5 overhead, or Kp 2 or 3 for a glow on the northern horizon. For the northern US, southern Canada and much of England and central Europe, plan on about Kp 5 to 7 for aurora low on the horizon. These are guides, not minimums: displays are sometimes seen at lower Kp, and a high Kp does not guarantee one.
- What Kp measures
- Why it depends on where you live
- Kp needed for major cities
- Overhead vs on the horizon
- Beyond Kp
- Find your own number
What the Kp index measures
The Kp index is a scale from 0 to 9 that describes how disturbed Earth’s magnetic field is. Each value is derived from standardized K indices at 13 geomagnetic observatories and covers a three-hour period, so it is a global measure, not a reading of the aurora over your house. Kp 0 to 2 is quiet, Kp 3 and 4 are unsettled to active, and Kp 5 or higher counts as a geomagnetic storm. NOAA turns that into its G-scale: Kp 5 is G1 (minor), Kp 6 is G2, Kp 7 is G3, Kp 8 (including 9-) is G4, and Kp 9 is G5 (extreme).
Why the Kp you need depends on where you live
Aurora forms in a ring around each magnetic pole called the auroral oval. When Kp rises, the oval swells and its edge moves toward the equator. How far you are from the oval is set by your geomagnetic latitude, which describes your position relative to Earth’s magnetic poles rather than the geographic equator. Geomagnetic latitude is measured in a coordinate system built on Earth’s magnetic field, and the magnetic pole is not at the geographic pole, so two cities at the same ordinary latitude can need different Kp values.
A commonly used rule of thumb puts the equatorward edge of the oval at about 66.5 degrees of geomagnetic latitude at Kp 0, moving roughly 2 degrees closer to the equator for each Kp step. It is a statistical average, not a fixed boundary: the oval changes shape through the night and from storm to storm. The same idea applies around the South Pole.
Kp needed for major cities
The tables below give model estimates, not observed minimums or forecasts. For each city, aurora low on the horizon is the Kp at which you might expect a glow near the northern horizon (southern horizon in the southern hemisphere), and aurora overhead is the Kp at which the oval’s edge is estimated to reach your sky. Both use the same estimate as the northern lights forecast.
1. We approximate each city’s geomagnetic latitude with a simple tilted-dipole model of Earth’s field, with the magnetic pole near 80.7°N, 72.7°W. This is an approximation, not a full magnetic-field model, so the latitudes can be off by a degree or two.
2. We estimate the Kp at which the oval’s edge reaches the city as (66.5 minus the geomagnetic latitude) divided by 2.03, rounded up. That is the “overhead” column.
3. For the “horizon” column we subtract two Kp steps, about 4 degrees or 450 km of latitude. That gap is an assumption about how far away aurora can be seen low on the horizon, not a measured law.
Example: Calgary’s geomagnetic latitude is about 57.5°, so (66.5 − 57.5) ÷ 2.03 is about 4.4, which rounds up to Kp 5 overhead and Kp 3 on the horizon.
| City | Approx. geomagnetic latitude | Kp for aurora low on the horizon | Kp for aurora overhead |
|---|---|---|---|
| Fairbanks, Alaska | 65.6° N | 1 | 1 |
| Yellowknife, Canada | 68.6° N | 1 | 1 |
| Anchorage, Alaska | 61.9° N | 1 | 3 |
| Edmonton, Canada | 60.1° N | 2 | 4 |
| Calgary, Canada | 57.5° N | 3 | 5 |
| Winnipeg, Canada | 58.2° N | 3 | 5 |
| Vancouver, Canada | 54.6° N | 4 | 6 |
| Montreal, Canada | 54.8° N | 4 | 6 |
| Toronto, Canada | 52.9° N | 5 | 7 |
| Seattle, USA | 53.1° N | 5 | 7 |
| Minneapolis, USA | 53.6° N | 5 | 7 |
| Chicago, USA | 50.8° N | 6 | 8 |
| Boston, USA | 51.7° N | 6 | 8 |
| New York, USA | 50.0° N | 7 | 9 |
| Denver, USA | 47.4° N | 8 | Beyond 9 |
| City | Approx. geomagnetic latitude | Kp for aurora low on the horizon | Kp for aurora overhead |
|---|---|---|---|
| Tromsø, Norway | 67.5° N | 1 | 1 |
| Reykjavik, Iceland | 68.9° N | 1 | 1 |
| Rovaniemi, Finland | 63.6° N | 1 | 2 |
| Inverness, Scotland | 59.8° N | 2 | 4 |
| Oslo, Norway | 59.7° N | 2 | 4 |
| Edinburgh, Scotland | 58.1° N | 3 | 5 |
| Stockholm, Sweden | 58.0° N | 3 | 5 |
| Helsinki, Finland | 57.7° N | 3 | 5 |
| Dublin, Ireland | 56.1° N | 4 | 6 |
| London, England | 53.4° N | 5 | 7 |
| Berlin, Germany | 52.2° N | 6 | 8 |
| Paris, France | 50.4° N | 6 | 8 |
| City | Approx. geomagnetic latitude | Kp for aurora low on the horizon | Kp for aurora overhead |
|---|---|---|---|
| Hobart, Australia | 49.7° S | 7 | 9 |
| Dunedin, New Zealand | 49.4° S | 7 | 9 |
| Christchurch, New Zealand | 46.8° S | 8 | Beyond 9 |
They are model estimates, and the real answer varies from storm to storm, so treat each as a planning value that could easily be off by a Kp step or more. NOAA’s examples describe where aurora has been seen, not the Kp at which you should expect it. For instance, aurora has been documented as far south as New York during G2 (Kp 6) storms, a step below this table’s horizon figure for New York, so the table is not a firm minimum.
“Beyond 9” means the simplified model puts the oval out of reach even at Kp 9, not that aurora there is impossible. The southern hemisphere figures are the roughest, and observers in Tasmania and southern New Zealand report aurora in moderate storms, often at lower Kp than this model suggests.
Aurora overhead versus aurora on the horizon
Aurora forms 100 kilometres or more above the ground, so it can be seen from hundreds of kilometres away. Our horizon column assumes that is about two Kp steps (roughly 450 km) short of the oval, which is a rule of thumb rather than a measured limit. From a city south of the oval you usually see a green glow low in the north, with rays and curtains reaching upward in stronger displays. Aurora directly overhead needs the oval itself to move over you, which takes a bigger storm.
That is why a moderate storm can produce good photos from places that would never see aurora overhead. A clear, dark poleward horizon can improve your chances substantially, even though activity and brightness still matter.
Why Kp alone is not enough
Reaching your Kp does not guarantee a display. The same Kp can look very different depending on storm structure, local time, auroral brightness, cloud and where you stand. Check these as well:
- Bz and solar wind speed. A sustained southward Bz and a fast solar wind generally let more energy into Earth’s magnetic field. They are important short-term indicators that activity may rise, though no single reading guarantees a display.
- Cloud cover. Cloud hides the aurora completely, so a clear sky at a lower Kp beats a cloudy night at a higher one.
- Darkness and the Moon. A dark sky greatly improves what you can see, and a bright Moon washes out faint displays, although strong aurora can still show in twilight or moonlight.
- Timing. Kp is averaged over three hours, and aurora can flare and fade within that block. Activity often peaks within a couple of hours of local midnight, though strong displays can occur at other times.
- Your horizon. Light pollution, hills and buildings on the poleward side all reduce what you can see.
How to find the Kp you need for your own city
The quickest way is to enter your city in the northern lights forecast. It shows an estimate of the Kp your city needs and compares it with tonight’s conditions. For the next few nights, use the 3-day northern lights forecast, which checks the Kp forecast against cloud cover and darkness.
If Kp is below your number, don’t give up automatically. Displays are sometimes seen at lower Kp than the tables suggest, especially from a dark site with a clear poleward horizon. For a direct look at where the aurora is right now, check NOAA’s 30-minute aurora forecast.
Key takeaways
- The farther you live from the magnetic pole, the higher the Kp you need.
- In our model, aurora on the horizon needs about two Kp steps less than aurora overhead.
- The city numbers are model estimates, not guaranteed minimums.
- Kp 5 (G1) is the first storm level, and it can bring aurora to the northern US and southern Canada low on the horizon.
- Cloud, darkness and Bz decide whether a good Kp turns into a good night.