OPEN RESEARCH DATA
City-by-city aurora Kp visibility thresholds
This table estimates how strong the planetary Kp index needs to be before an aurora may appear low on the poleward horizon, or directly overhead, in each covered city. It is a planning baseline—not a sighting guarantee—and is published in reusable formats so journalists, trip planners and researchers can check or cite the values.
How to read the table
- Horizon Kp is the estimated level at which a faint glow may reach the poleward horizon under dark, clear skies.
- Overhead Kp is the estimated level at which the auroral oval reaches the city's geomagnetic latitude.
- Lower values indicate that a location more often sits near or inside the auroral oval. Values are rounded to one decimal place.
- 0.0 means the threshold is already met at the calmest possible conditions (Kp 0), since Kp cannot go lower; 9.0 means it is not reached even at the most extreme storm level (Kp 9), the maximum the index goes to.
Cloud, daylight, moonlight and the real shape of the auroral oval can still prevent a sighting. Kp is planetary rather than local, so use each city's live forecast page for the current NOAA OVATION oval, darkness and solar-wind context.
All city thresholds
| City | Country | Geomag. lat. | Horizon Kp | Overhead Kp |
|---|---|---|---|---|
| Akureyri | Iceland | 69.70°N | 0.0 | 0.0 |
| Alta | Norway | 67.13°N | 0.0 | 0.0 |
| Churchill | Canada | 67.19°N | 0.0 | 0.0 |
| Inuvik | Canada | 71.12°N | 0.0 | 0.0 |
| Longyearbyen | Svalbard | 75.25°N | 0.0 | 0.0 |
| Nuuk | Greenland | 72.57°N | 0.0 | 0.0 |
| Tromsø | Norway | 67.46°N | 0.0 | 0.0 |
| Utqiaġvik | United States | 70.06°N | 0.0 | 0.0 |
| Vík | Iceland | 67.72°N | 0.0 | 0.0 |
| Yellowknife | Canada | 68.56°N | 0.0 | 0.0 |
| Abisko | Sweden | 66.30°N | 0.0 | 0.1 |
| Bodø | Norway | 65.98°N | 0.0 | 0.2 |
| Fairbanks | United States | 65.64°N | 0.0 | 0.4 |
| Kiruna | Sweden | 65.64°N | 0.0 | 0.4 |
| Ivalo | Finland | 65.33°N | 0.0 | 0.6 |
| Reykjavík | Iceland | 65.00°N* | 0.0 | 0.7 |
| Murmansk | Russia | 64.86°N | 0.0 | 0.8 |
| Tórshavn | Faroe Islands | 64.47°N | 0.0 | 1.0 |
| Whitehorse | Canada | 63.83°N | 0.0 | 1.3 |
| Rovaniemi | Finland | 63.58°N | 0.0 | 1.4 |
| Luleå | Sweden | 63.25°N | 0.0 | 1.6 |
| Trondheim | Norway | 63.04°N | 0.0 | 1.7 |
| Nome | United States | 62.55°N | 0.0 | 1.9 |
| Oulu | Finland | 62.23°N | 0.0 | 2.1 |
| Anchorage | United States | 61.91°N | 0.0 | 2.2 |
| Umeå | Sweden | 61.88°N | 0.0 | 2.2 |
| Lerwick | United Kingdom | 61.81°N | 0.0 | 2.3 |
| Juneau | United States | 61.63°N | 0.0 | 2.4 |
| Bergen | Norway | 60.99°N | 0.2 | 2.7 |
| Thurso | United Kingdom | 60.72°N | 0.4 | 2.8 |
| Edmonton | Canada | 60.05°N | 0.7 | 3.1 |
| Kuopio | Finland | 59.90°N | 0.8 | 3.2 |
| Inverness | United Kingdom | 59.77°N | 0.8 | 3.3 |
| Oslo | Norway | 59.67°N | 0.9 | 3.3 |
| Saskatoon | Canada | 59.47°N | 1.0 | 3.4 |
| Aberdeen | United Kingdom | 59.11°N | 1.2 | 3.6 |
| Glasgow | United Kingdom | 58.23°N | 1.6 | 4.0 |
| Edinburgh | United Kingdom | 58.14°N | 1.6 | 4.1 |
| Winnipeg | Canada | 58.17°N | 1.6 | 4.1 |
| Stockholm | Sweden | 57.96°N | 1.7 | 4.2 |
| Helsinki | Finland | 57.72°N | 1.8 | 4.3 |
| Calgary | Canada | 57.53°N | 1.9 | 4.4 |
| Belfast | United Kingdom | 57.28°N | 2.0 | 4.5 |
| Thunder Bay | Canada | 57.21°N | 2.1 | 4.5 |
| Newcastle | United Kingdom | 56.95°N | 2.2 | 4.6 |
| Tallinn | Estonia | 57.04°N | 2.2 | 4.6 |
| Saint Petersburg | Russia | 56.69°N | 2.3 | 4.8 |
| Dublin | Ireland | 56.13°N | 2.6 | 5.0 |
| St. John's | Canada | 56.18°N | 2.6 | 5.0 |
| Québec City | Canada | 56.11°N | 2.6 | 5.1 |
| Manchester | United Kingdom | 55.62°N | 2.9 | 5.3 |
| Sudbury | Canada | 55.67°N | 2.8 | 5.3 |
| Copenhagen | Denmark | 55.34°N | 3.0 | 5.4 |
| Duluth | United States | 55.45°N | 2.9 | 5.4 |
| Marquette | United States | 55.47°N | 2.9 | 5.4 |
| Fargo | United States | 55.20°N | 3.1 | 5.5 |
| Montréal | Canada | 54.80°N | 3.3 | 5.7 |
| Ottawa | Canada | 54.71°N | 3.3 | 5.7 |
| Riga | Latvia | 54.76°N | 3.3 | 5.7 |
| Vancouver | Canada | 54.60°N | 3.4 | 5.8 |
| Bangor | United States | 54.08°N | 3.6 | 6.0 |
| Burlington | United States | 53.78°N | 3.8 | 6.2 |
| Halifax | Canada | 53.81°N | 3.7 | 6.2 |
| Hamburg | Germany | 53.71°N | 3.8 | 6.2 |
| Hobart | Australia | 53.70°S* | 3.8 | 6.2 |
| Spokane | United States | 53.78°N | 3.8 | 6.2 |
| Minneapolis | United States | 53.57°N | 3.9 | 6.3 |
| Amsterdam | Netherlands | 53.39°N | 3.9 | 6.4 |
| London | United Kingdom | 53.37°N | 4.0 | 6.4 |
| Seattle | United States | 53.07°N | 4.1 | 6.5 |
| Toronto | Canada | 52.88°N | 4.2 | 6.6 |
| Bozeman | United States | 52.61°N | 4.3 | 6.8 |
| Vilnius | Lithuania | 52.40°N | 4.4 | 6.9 |
| Berlin | Germany | 52.17°N | 4.5 | 7.0 |
| Boston | United States | 51.66°N | 4.8 | 7.2 |
| Moscow | Russia | 51.65°N | 4.8 | 7.2 |
| Detroit | United States | 51.45°N | 4.9 | 7.3 |
| Chicago | United States | 50.81°N | 5.2 | 7.6 |
| Portland | United States | 50.98°N | 5.1 | 7.6 |
| Warsaw | Poland | 50.68°N | 5.3 | 7.7 |
| Invercargill | New Zealand | 50.24°S | 5.5 | 7.9 |
| Des Moines | United States | 50.17°N | 5.5 | 8.0 |
| New York | United States | 50.01°N | 5.6 | 8.0 |
| Omaha | United States | 49.68°N | 5.8 | 8.2 |
| Prague | Czechia | 49.64°N | 5.8 | 8.2 |
| Dunedin | New Zealand | 49.39°S | 5.9 | 8.3 |
| Queenstown | New Zealand | 48.84°S | 6.2 | 8.6 |
| Launceston | Australia | 48.25°S | 6.5 | 8.9 |
| Adelaide | Australia | 42.71°S | 9.0 | 9.0 |
| Auckland | New Zealand | 39.90°S | 9.0 | 9.0 |
| Christchurch | New Zealand | 46.77°S | 7.2 | 9.0 |
| Denver | United States | 47.39°N | 6.9 | 9.0 |
| Melbourne | Australia | 44.92°S | 8.1 | 9.0 |
| Perth | Australia | 41.13°S | 9.0 | 9.0 |
| Punta Arenas | Chile | 43.87°S | 8.6 | 9.0 |
| Salt Lake City | United States | 47.66°N | 6.7 | 9.0 |
| Stanley | Falkland Islands | 42.65°S | 9.0 | 9.0 |
| Sydney | Australia | 40.29°S | 9.0 | 9.0 |
| Ushuaia | Argentina | 45.52°S | 7.8 | 9.0 |
| Wellington | New Zealand | 44.24°S | 8.4 | 9.0 |
* Uses a cross-checked geomagnetic latitude correction; the JSON and CSV include a boolean flag for these rows.
Methodology and reproducibility
Geographic coordinates come from the site's curated city records. Geomagnetic latitude is calculated at build time with a centred-dipole approximation, with documented cross-checked corrections in regions where that approximation performs poorly. The Kp thresholds are then solved against the same continuous Kp-to-auroral-latitude fit used by Aurora Tonight's live verdict. The horizon estimate applies a fixed poleward visibility margin before solving the same relationship.
The transformation code and its limitations are described on the data sources and methodology page. Threshold values are rebuilt from the source city coordinates whenever the site is published, keeping the HTML, JSON, CSV and individual city pages in sync.
Responsible use
Treat these values as comparative planning estimates. They do not account for local cloud, terrain, artificial light, moment-to-moment substorms or every variation in Earth's magnetic field. Do not use this dataset for safety-critical navigation or operational space-weather decisions; consult official agencies for those purposes.