Is Tromsø or Reykjavík better for the northern lights?

Reykjavík sits closer to the oval, at 68.8 degrees geomagnetic against 67.5. 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, Tromsø or Reykjavík?

Tromsø, with 19.2 hours of civil night on December 15 against 17.0 in Reykjavík.

What Kp do Tromsø and Reykjavík need?

By SWPC's rule of 66 degrees at Kp 0 and 2 degrees per step, Tromsø needs about Kp 0 and Reykjavík Kp 0 for the average oval edge to sit overhead.

When is it too light for aurora in Tromsø and Reykjavík?

Tromsø: April 27 to August 14. Reykjavík: May 17 to July 25.

Which is clearer, Tromsø or Reykjavík?

Reykjavík, with 79% mean cloud in the months with 4 hours or more of civil night against 83% in Tromsø (NASA POWER, 2001 to 2020).

Comparison

Tromsø vs Reykjavík for the northern lights

Answer

Reykjavík sits 1.3 degrees higher on the IGRF-14 dipole, 68.8 against 67.5. By SWPC's oval-edge rule Reykjavík needs about Kp 0 for the average edge to sit overhead and Tromsø Kp 0. That reverses the map, where Tromsø is 5.5 degrees closer to the pole.

67.5° / 68.8°

dipole latitude

Side by side

Computed figures for both towns
Figure	Tromsø	Reykjavík
Dipole latitude	67.5°	68.8°
Kp for the oval edge overhead	Kp 0	Kp 0
Civil night, December 15	19.2 h	17.0 h
Dark-season days	239	269
Nights with no civil darkness	110	70
Dark-month cloud, NASA POWER	83%	79%
Solar midnight, December 15	23:39	01:23

Tromsø sits at 67.5 degrees geomagnetic, inside SWPC's 60 to 75 degree band, where aurora can be seen on more than half of all nights. No storm is needed: by SWPC's rule the average oval edge is overhead at Kp 0. Reykjavík sits at 68.8 degrees geomagnetic, inside SWPC's 60 to 75 degree band, where aurora can be seen on more than half of all nights. No storm is needed: by SWPC's rule the average oval edge is overhead at Kp 0.

Civil night month by month

On December 15 Tromsø has 19.2 hours of civil night and Reykjavík 17.0. Across the 15th of each month, Tromsø is darker in 5 months and Reykjavík in 5. The widest gap comes in August, when Reykjavík has 4.7 more hours.

Hours of civil night on the 15th of each month, 2026
Month	Tromsø	Reykjavík	Difference
January	17.8 h	16.1 h	+1.7 h
February	14.0 h	13.5 h	+0.5 h
March	10.2 h	10.5 h	-0.3 h
April	4.8 h	6.8 h	-2.0 h
May	0.0 h	1.2 h	-1.2 h
June	0.0 h	0.0 h	+0.0 h
July	0.0 h	0.0 h	+0.0 h
August	0.6 h	5.3 h	-4.7 h
September	8.4 h	9.2 h	-0.8 h
October	12.7 h	12.5 h	+0.2 h
November	16.6 h	15.4 h	+1.2 h
December	19.2 h	17.0 h	+2.2 h

Difference: Tromsø minus Reykjavík. Each figure links to that town's month page.

Season and midnight sun

Tromsø has no civil darkness from April 27 to August 14, 110 nights in 2026, and its dark season, 4 or more evening hours of civil night, lasts 239 days. Reykjavík has no civil darkness from May 17 to July 25, 70 nights in 2026, and its dark season, 4 or more evening hours of civil night, lasts 269 days.

Distance, cloud and time zones

The two towns are 1,844 km apart by great circle. In the dark months Reykjavík averages 79% cloud and Tromsø 83%, from NASA POWER's 2001 to 2020 record. Tromsø's best month by civil night times clear sky is January. Reykjavík's best month by civil night times clear sky is December. Time zones: Europe/Oslo and Atlantic/Reykjavik.

For tonight, open the live pages for Tromsø and Reykjavík, which carry the live OVATION cell.

Questions

Is Tromsø or Reykjavík better for the northern lights?: Reykjavík sits closer to the oval, at 68.8 degrees geomagnetic against 67.5. 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, Tromsø or Reykjavík?: Tromsø, with 19.2 hours of civil night on December 15 against 17.0 in Reykjavík.
What Kp do Tromsø and Reykjavík need?: By SWPC's rule of 66 degrees at Kp 0 and 2 degrees per step, Tromsø needs about Kp 0 and Reykjavík Kp 0 for the average oval edge to sit overhead.
When is it too light for aurora in Tromsø and Reykjavík?: Tromsø: April 27 to August 14. Reykjavík: May 17 to July 25.
Which is clearer, Tromsø or Reykjavík?: Reykjavík, with 79% mean cloud in the months with 4 hours or more of civil night against 83% in Tromsø (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.