Best time to see the northern lights

Why darkness is the first constraint

Aurora happens continuously - it does not stop for summer. The problem is visibility. Above the Arctic Circle, summer brings midnight sun: the sky stays bright for weeks without a true night. Aurora at Kp 5 is present but completely invisible against a bright sky. Darkness is the starting point for any viable aurora observation.

The practical aurora season begins when astronomical twilight ends - when the sun drops more than 18° below the horizon and the sky reaches true darkness. In Tromsø, this returns in late August. In Scotland, it never entirely disappears even in mid-summer, but the nights get short enough in June and July that aurora watching is not viable.

Polar night - when the sun does not rise at all above the Arctic Circle - runs roughly from November to January at 70°N. This gives 24-hour darkness and removes timing pressure entirely: aurora at 2 pm on a cloudy afternoon is possible in theory. But continuous darkness does not mean better aurora; that depends on solar activity, not the length of the night.

The equinox effect

Statistical analysis across multiple solar cycles consistently shows that geomagnetic activity peaks close to the equinoxes, in March and September. This is called the Russell-McPherron effect. Around the equinoxes, Earth's magnetic field is oriented in a way that allows the solar wind's southward-pointing magnetic field component to couple more efficiently into the magnetosphere. The result: more geomagnetic storms for a given level of solar activity.

The effect isn't perfectly symmetric between the two equinoxes, and not even across the two months most associated with it: March and October show the highest average activity in this site's own historical data, while September - despite equinox timing - sits mid-pack among the seven in-season months rather than among the leaders. The gap between March and October and most of the rest of the season is itself within year-to-year variation, so none of this is reliable enough to plan a trip around. What is reliable, and what the next section is actually about, is the difference between being inside this broader season and outside it.

How the months compare

Here's the number that matters most for planning: not which month inside the season you pick, but whether you're in the season at all. Aurora season in the tracked data runs from September to March. Within it, average nights per month range narrowly - from 9.2 up to 11.5 a month across 15 years of data - and only the top of that range (March and October) and the bottom of it (December and January) are far enough apart to call a real difference. Every month in between sits inside the same statistical noise as its neighbours.

Leave the season, and the picture changes sharply. April drops to an average of 4.5 nights - several times the size of the season's own year-to-year variation, and the only completely unambiguous pattern in the twelve months below. Trip length, destination latitude, and cloud cover affect your odds of seeing something far more than which in-season month you choose.

*Average aurora nights per month, across 308 tracked northern hemisphere locations (minKp 1 to 8 depending on latitude), from aurora-history.json (15 years of geomagnetic data, 2010-2024). Shown in calendar order, not ranked - the highlighted months are the September-to-March season described above. This is a sitewide average across many locations and thresholds, not a figure for any single place - check your destination's own page for its specific numbers.

Month by month breakdown

The solar cycle factor

We are currently near solar maximum - the peak of Solar Cycle 25, expected to hold elevated activity through 2025-2026. Solar maximum produces more coronal mass ejections (CMEs), stronger flares, and higher baseline geomagnetic activity than solar minimum years. The difference is significant.

During solar minimum (roughly 2018-2020), a Kp 5 storm occurred perhaps 30-40 times per year globally. During solar maximum, Kp 5+ events occur 80-100+ times annually, and extreme events like the G5 storm of May 2024 - visible across the UK, Europe, and the northern USA - are possible where they would be rare at solar minimum.

Practically, this means the 2024-2026 window is an exceptionally good time to plan an aurora trip. Search flights to Reykjavik on Aviasales early - October and February dates fill fast. Locations that rarely see aurora - Scotland, northern England, the Netherlands - are seeing regular displays. High-latitude destinations like Tromsø and Saariselkä are seeing aurora at unusually high frequencies even in low-Kp conditions.

Aurora australis - southern hemisphere season

Aurora australis follows the same solar physics as aurora borealis - both respond to the same geomagnetic storms. The difference is season. When the northern hemisphere is in summer (May to August), the southern hemisphere is in winter, and the austral winter is when most New Zealand and Tasmania trips are planned for darkness.

Averaged across every southern hemisphere location this site tracks, activity rises near both equinoxes (currently strongest around September and March) and dips both in southern winter (June-July) and around the January and December turn of the year. That gap between the strongest and weakest months is real, but the leading months themselves aren't reliably distinguishable from each other - unlike the north, there's no month here that clears a real, unambiguous lead over its closest rivals. Southern locations also need a higher minimum Kp than many northern ones (Kp 3 at the lowest tracked here, against Kp 1 in parts of the Arctic), which makes them more dependent on active geomagnetic storms - inherently noisier year to year than the steady background activity driving high-latitude northern counts. That's the main reason the southern picture is less clear-cut than the northern one; the smaller tracked network (50 locations against 308) adds a little more noise on top, but isn't the primary driver.

*Average aurora nights per month, across 50 tracked southern hemisphere locations, from the same 15-year dataset. Shown in calendar order, not ranked - southern coverage is thinner than northern coverage and, as above, doesn't support ranking specific months against each other. This is a sitewide average, not a figure for any single place.

Lake Tekapo in New Zealand and Hobart in Tasmania are the most accessible southern aurora destinations. The Aoraki Mackenzie Dark Sky Reserve around Lake Tekapo is one of the best dark-sky viewing areas in the world.

Practical recommendation