ToolComputedCited
Which month is best for aurora where I live?
Answer
| Month | Civil night | Cloud | Score | Days at Kp 5+ |
|---|---|---|---|---|
| January | 14.9 h | 84% | 2.4 h | 6% |
| February | 13.0 h | 82% | 2.3 h | 8% |
| March | 10.8 h | 74% | 2.8 h | 12% |
| April | 8.1 h | 65% | 2.8 h | 12% |
| May | 5.3 h | 67% | 1.8 h | 10% |
| June | 3.3 h | 68% | 1.1 h | 8% |
| July | 4.4 h | 67% | 1.4 h | 9% |
| August | 7.1 h | 70% | 2.1 h | 11% |
| September | 9.8 h | 71% | 2.8 h | 14% |
| October | 12.2 h | 75% | 3.1 h | 12% |
| November | 14.4 h | 82% | 2.6 h | 10% |
| December | 15.6 h | 85% | 2.3 h | 5% |
Worked example
Fairbanks: civil night on the 15th runs from 0.0 hours in May to 17.2 hours in December. NASA POWER puts mean cloud at 55% in January, which gives it the best score of 7.3 clear-dark hours.
December has more night, 17.2 hours, but 59% cloud against 55% puts January ahead. The score is a way to compare months, not a count of hours you will see aurora.
How the score works
Glow computes civil night, the sun at -6 degrees or lower, on the 15th of each month for your coordinates with SunCalc. It multiplies that by one minus NASA POWER's mean cloud amount for the month. A month with 16 hours of night and 80% cloud scores 3.2; a month with 10 hours and 50% cloud scores 5.0.
NASA POWER's cloud amount is a mean over all hours, day and night. Glow uses the value of the Glow town that shares your 1 degree cell. Outside those cells there is no cloud value, and the ranking falls back to darkness alone.
Where activity comes in
The last column counts, for each calendar month from 1996 to 2025, the share of UTC days whose highest 3-hour Kp reached the level that puts SWPC's average oval edge over your latitude. It is not in the score, because it varies less between months than darkness and cloud.
SWPC says: "The best Seasons for aurora watching are around the spring and fall equinoxes." The Kp column shows how much that holds for your level.
Questions
- What is the best month to see the northern lights?
- It depends on where you are. Far north, the dark months are also the cloudiest in many places, so a month either side of midwinter can score better. The tool ranks all 12 for your coordinates.
- Is the score a forecast?
- No. It combines computed darkness with a 20-year cloud average. Activity on any night is only known hours ahead.
- Why is cloud missing for my point?
- Glow stores NASA POWER values only for the 1 degree cells that hold its towns. Pick a nearby town from the search to use its cell.
- Does the moon count?
- No. The moon changes from year to year; use the moon planner once you have picked a month.