Iceland · aurora forecast for the nights ahead AuroraRadar.pro

For every hour of the night we multiply four things: aurora activity (from the Kp forecast), clear sky, darkness (whether the sun is low enough yet) and the moon (the brighter and higher it is, the fainter the aurora you can see; below the horizon it doesn’t matter). A spot’s score is its best hour; the “best time” is the hours when the score stays close to that peak. 100 means a perfect night, which almost never happens. The region score is the score of the best spot in that region – because that’s where it’s worth going – and the description adds how much cloud hangs over the rest of the region. Spots in towns get an extra light-pollution factor (e.g. Reykjavík 0.66, Akureyri 0.54), because you won’t see a faint aurora under street lights.

The overnight forecast is based on Kp, which is a 3-hour average for the whole planet and lags behind what’s happening above your head. That’s why for the current hour we also work out a “now” score: from the solar wind measurements (Bz, Bt, speed, density) we estimate an equivalent Kp using the Newell coupling function (2007) – the more southward the Bz, the stronger the field and the faster the wind, the more energy pours into the magnetosphere – and plug it into the same formula with clouds, darkness, moon and light pollution. It’s an estimate for the next 30–60 minutes, because that’s how long the wind takes to travel from the spacecraft to Earth. The night score tells you whether to plan a trip; the “now” score tells you whether to step outside right now. After dark the same reading also counts on the map, in the ranking and on the chart: the current hour of tonight takes its Kp from the solar wind instead of the forecast, so a sudden jump in activity shows up straight away in the region colours.

A planetary index calculated every 3 hours from a worldwide network of magnetometers (GFZ Potsdam); NOAA publishes a forecast of it for the coming days. The higher the Kp, the further south the auroral oval reaches. Iceland sits right under the oval, so even Kp 1–2 gives you a chance with clear skies; at Kp 3–4 the aurora is overhead; from Kp 5 we’re talking about a geomagnetic storm (G1–G5 scale), visible even from Scotland or the northern US.

Remember: Kp is a 3-hour average for the whole planet. The aurora can “explode” for fifteen minutes even at a low Kp – that’s why we show the live “now” reading next to the forecast.

Veðurstofa Íslands publishes its own 0–9 number for every night, 10 days ahead, based on the NOAA forecast and local experience. It roughly matches the expected Kp: 0–1 quiet, 2–3 aurora visible with clear skies, 4–5 bright and moving, 6+ storm. Icelanders read this number together with the IMO cloud map – which is exactly what we combine into one score.

The north–south component of the magnetic field carried by the solar wind. When it’s negative (“southward”), it links up with Earth’s field and lets energy into the magnetosphere – that’s when the aurora grows. A positive Bz shuts the door. It changes minute by minute, so Bz is the one to watch once you’re already out under the sky.

The total strength of the field (Bz is part of it). A high Bt means big potential – but only if Bz turns south. Typically 3–8 nT; when a coronal mass ejection (CME) passes, it can jump to 20–40 nT.

Speed tells you how fast the particles hit the magnetosphere; a fast stream (from a coronal hole or a CME) delivers more energy. Density is the number of protons per cubic centimetre – dense wind gives a brighter, “juicier” aurora, as long as Bz plays along.

NOAA’s OVATION model estimates every 5 minutes how many gigawatts of energy the aurora is dumping into the upper atmosphere of the northern hemisphere. It’s the simplest single number for “how much aurora is there right now” – about 30–60 minutes ahead, because the model works from solar wind measured before it reaches Earth.

The solar wind is measured by a NOAA spacecraft at the L1 point, about 1.5 million km upstream of Earth. At a typical 400 km/s, the same bit of wind reaches us about an hour later; at 800 km/s – half an hour later. So “now” on this page is really a forecast for the next half hour to an hour.

An hourly forecast from MET Norway for every spot, in three layers – just like the “lower / middle / high” tabs on the vedur.is cloud maps. Low and middle clouds block the aurora completely and count in full; high clouds (cirrus) let a bright aurora through, so they count half. The percentage is how much of the sky is covered. Aurora activity is almost the same across the whole country, so it’s the clouds that decide where to go.

After sunset the sun sinks below the horizon in stages: civil twilight (0 to −6°), nautical (−6 to −12°) and astronomical (−12 to −18°). You’ll see a faint aurora only from nautical twilight, and properly from astronomical. The score works out the sun’s height hour by hour for every spot and counts darkness gradually: 15–50 % in civil twilight, 50–100 % in nautical, and in full from −12°. Twilight hours are hatched on the chart. In Iceland there’s no full darkness at all from mid-May to the end of July, while in December it lasts from about 17:00 to 9:00.

How much of the disc is lit, and when the moon rises or sets. A full moon brightens the sky and drowns out a faint aurora (a strong one doesn’t care), but it lights up the landscape beautifully for photos. It’s not just the phase that matters, but whether the moon is actually in the sky – the score checks that hour by hour for every spot: below the horizon the moon doesn’t count at all, and low down (under 10°) only a little.

Sky brightness overhead from a light-pollution atlas, modelled from VIIRS satellite images of night-time lights from 2025. The higher the number, the darker: a natural sky with no artificial light is about 22.0 mag/arcsec², suburbs about 20, a city centre below 19. It’s a model, not a measurement, and it describes the sky overhead – the glow low above the horizon towards a town can be brighter. The score turns this number into a light-pollution factor: no penalty down to about 21.2, roughly half in a city centre. The “Dark sky” switch above the map shows the whole layer, and each spot’s card tells you where the nearest darker sky is.

Inside Iceland’s interior and over Vatnajökull the atlas shows a false glow from the glaciers (the satellite picks up reflections from snow and ice), so there we assume natural darkness.

The forecast temperature adjusted for wind (the wind chill formula used by weather services in Canada and the US). At −2 °C with a 10 m/s wind, it feels like about −11 °C. Wind is the norm on the Icelandic coast, so this number tells you more than the thermometer does.