Is Minneapolis or Thunder Bay better for the northern lights?

Thunder Bay sits closer to the oval, at 57.1 degrees geomagnetic against 53.5. Darkness, cloud and your dates decide the rest; the tables on this page show both towns month by month.

Which has longer nights in December, Minneapolis or Thunder Bay?

Thunder Bay, with 14.3 hours of civil night on December 15 against 14.0 in Minneapolis.

What Kp do Minneapolis and Thunder Bay need?

By SWPC's rule of 66 degrees at Kp 0 and 2 degrees per step, Minneapolis needs about Kp 7 and Thunder Bay Kp 5 for the average oval edge to sit overhead.

When is it too light for aurora in Minneapolis and Thunder Bay?

Minneapolis: never, every night has civil darkness. Thunder Bay: never, every night has civil darkness.

Which is clearer, Minneapolis or Thunder Bay?

Minneapolis, with 59% mean cloud in the months with 4 hours or more of civil night against 70% in Thunder Bay (NASA POWER, 2001 to 2020).

Comparison

Minneapolis vs Thunder Bay for the northern lights

Answer

Thunder Bay sits 3.6 degrees higher on the IGRF-14 dipole, 57.1 against 53.5. By SWPC's oval-edge rule Thunder Bay needs about Kp 5 for the average edge to sit overhead and Minneapolis Kp 7. On the map Thunder Bay is also closer to the pole, by 3.4 degrees.

53.5° / 57.1°

dipole latitude

Side by side

Computed figures for both towns
Figure	Minneapolis	Thunder Bay
Dipole latitude	53.5°	57.1°
Kp for the oval edge overhead	Kp 7	Kp 5
Civil night, December 15	14.0 h	14.3 h
Dark-season days	365	365
Nights with no civil darkness	0	0
Dark-month cloud, NASA POWER	59%	70%
Solar midnight, December 15	00:08	00:52

Minneapolis sits at 53.5 degrees geomagnetic. The lowest NOAA storm level whose typical viewing latitude reaches it is G3 (Kp = 7). By SWPC's rule the average oval edge is overhead only at Kp 7. Thunder Bay sits at 57.1 degrees geomagnetic. By SWPC's rule the average oval edge is overhead at Kp 5, and aurora is usually visible on the northern horizon at G1 (Kp 5) or less.

Civil night month by month

On December 15 Minneapolis has 14.0 hours of civil night and Thunder Bay 14.3. Across the 15th of each month, Minneapolis is darker in 6 months and Thunder Bay in 4. The widest gap comes in June, when Minneapolis has 0.6 more hours.

Hours of civil night on the 15th of each month, 2026
Month	Minneapolis	Thunder Bay	Difference
January	13.6 h	13.9 h	-0.3 h
February	12.4 h	12.6 h	-0.2 h
March	11.0 h	11.0 h	+0.0 h
April	9.3 h	9.1 h	+0.2 h
May	7.9 h	7.4 h	+0.5 h
June	7.0 h	6.4 h	+0.6 h
July	7.4 h	6.9 h	+0.5 h
August	8.8 h	8.4 h	+0.4 h
September	10.4 h	10.3 h	+0.1 h
October	12.0 h	12.0 h	+0.0 h
November	13.3 h	13.6 h	-0.3 h
December	14.0 h	14.3 h	-0.3 h

Difference: Minneapolis minus Thunder Bay. Each figure links to that town's month page.

Season and midnight sun

Minneapolis has some civil darkness every night of 2026, and clears Glow's 4-hour dark-season bar every evening. Thunder Bay has some civil darkness every night of 2026, and clears Glow's 4-hour dark-season bar every evening.

Distance, cloud and time zones

The two towns are 487 km apart by great circle. In the dark months Minneapolis averages 59% cloud and Thunder Bay 70%, from NASA POWER's 2001 to 2020 record. Minneapolis's best month by civil night times clear sky is September. Thunder Bay's best month by civil night times clear sky is January. Time zones: America/Chicago and America/Toronto.

For tonight, open the live pages for Minneapolis and Thunder Bay, which carry the live OVATION cell.

Questions

Is Minneapolis or Thunder Bay better for the northern lights?: Thunder Bay sits closer to the oval, at 57.1 degrees geomagnetic against 53.5. Darkness, cloud and your dates decide the rest; the tables on this page show both towns month by month.
Which has longer nights in December, Minneapolis or Thunder Bay?: Thunder Bay, with 14.3 hours of civil night on December 15 against 14.0 in Minneapolis.
What Kp do Minneapolis and Thunder Bay need?: By SWPC's rule of 66 degrees at Kp 0 and 2 degrees per step, Minneapolis needs about Kp 7 and Thunder Bay Kp 5 for the average oval edge to sit overhead.
When is it too light for aurora in Minneapolis and Thunder Bay?: Minneapolis: never, every night has civil darkness. Thunder Bay: never, every night has civil darkness.
Which is clearer, Minneapolis or Thunder Bay?: Minneapolis, with 59% mean cloud in the months with 4 hours or more of civil night against 70% in Thunder Bay (NASA POWER, 2001 to 2020).

Sources and verification

IGRF-14 coefficients, NOAA NCEIhttps://www.ngdc.noaa.gov/IAGA/vmod/coeffs/igrf14coeffs.txt
SunCalchttps://github.com/mourner/suncalc
GeoNameshttps://www.geonames.org/export/
NASA POWER climatologyhttps://power.larc.nasa.gov/docs/services/api/temporal/climatology/
NOAA SWPC, Tips on viewing the aurorahttps://www.spaceweather.gov/content/tips-viewing-aurora

Quoted figures last checked against their sources on 2026-09-30; next review 2026-12-31. Computed figures come from SunCalc and the IGRF-14 dipole as described in the methodology. Every quote is listed in the sources ledger.