Best Nights for the Northern Lights

Picking dates for an aurora trip

Book around the moon first. The week either side of a new moon gives the most moon-free darkness, and the calendar’s “darkest week” shows exactly where that falls at each place. Then stay long enough to beat the weather: three or four nights in one place gives you several chances at a gap in the cloud, which matters far more than any long-range activity outlook.

Season decides the rest. In Tromsø, Abisko and Rovaniemi the useful season runs from late August to early April; Reykjavík’s is slightly shorter at the ends; Fairbanks and Yellowknife run from late August to mid-April. September, October and March combine long-enough nights with the equinox boost and milder weather, which is why many guides call them the best months. December and January have the longest nights but more cloud on the Norwegian and Icelandic coasts, and very cold, clear spells inland in Lapland, Alaska and the Northwest Territories. For the southern lights from Tasmania, the long nights of May to August are best, with the March and September equinoxes again adding activity.

Once your dates are within a week, the aurora forecast for this week adds NOAA’s 3-day Kp forecast and the cloud forecast to the same places and names the best night at each. Check the night itself on the day: Will I see the northern lights tonight? compares NOAA’s 3-day Kp forecast with the Kp each latitude needs, and Aurora Tonight shows which live cameras are dark and clear right now.

Questions

Why does the moon matter for the northern lights?

Moonlight brightens the sky background, so faint aurora that would be obvious under a dark sky becomes hard to see, and photos lose contrast. A strong display still shows through a full moon. The useful number is how many dark hours have the moon below the horizon, not just its phase: a full moon that rises at 04:00 leaves the evening dark.

Are the equinoxes really better for aurora?

On average, yes. Geomagnetic storms are roughly twice as frequent in the weeks around the March and September equinoxes as around the solstices, because of how Earth’s magnetic field is tilted toward the solar wind’s field at those times of year (the Russell–McPherron effect). It raises the odds; it does not guarantee a display.

Can anyone forecast aurora 60 days ahead?

No. Darkness and the moon are certain and are what this calendar computes. Activity is not: NOAA’s 27-day outlook repeats the Sun’s last rotation, which catches recurring coronal-hole streams but not new eruptions, and Kp forecasts are only reliable a few days out.

What is the darkest week for an aurora trip?

For each place, the calendar marks the seven nights in the next 60 with the most hours that are both dark and moon-free. Around the new moon in midwinter that can be 15 hours a night in Tromsø or Fairbanks.