Northern lights forecast
for Porjus
Porjus, Sweden — about 64.8° geomagnetic latitude. In Swedish Lapland, between Gällivare and Jokkmokk. The Lulevatten lake, frozen solid in winter, opens a wide, flat plain.
Northern lights in Porjus tonight · live
Reading the field under the auroral oval…
How it works
A magnetometer measures the Earth’s magnetic field. When a substorm surges the electric current that runs about 100 km up along the auroral oval, the field on the ground beneath it drops by hundreds of nanotesla (nT) within minutes — the sharp dip a magnetogram shows.
This reads the nearest of the Finnish Meteorological Institute’s eight magnetometers, Muonio, against its own last 24 hours: 150 nT either way is active, a 300 nT drop a substorm, 600 a strong one. It measures the sky over the station — up to about 300 km away it still speaks for yours — and says nothing about cloud. Kp and Hp30 are planetary; this is local, and minutes old.
Where to look
From the lakeshore, face north; the flat, dark plain opens the horizon. Foreground: the ice and the treeline.
Can you see the aurora in Porjus?
Yes. From a dark site you need about Kp 2 for a faint glow low on the northern horizon, and roughly Kp 4 for bright aurora directly overhead. At 64.8° geomagnetic latitude Porjus sits on the edge of the oval — you want an active night.
Over the last 12 months the planetary Kp peaked at the levels Porjus needs on the days shown — out of 365. Kp is a global index, so these are the odds the sky was active enough; you still need clear, dark skies here. In 94 years on record the strongest day hit Kp 9.
The greatest storms on record: The Halloween storms (Oct 2003) · The Gannon storm (May 2024) · 13 Nov 1960
The full Kp archive, 1932 → today →When to go
The season runs late August to mid April, when the nights are long and dark. You also need clear skies and a low moon — even a strong Kp is useless under cloud. Check tonight's live call above, then plan a night around the dark window, cloud and moon.
Clearest dark months here (outlined): Mar, Sep, Oct. Faint: no night with an hour of astronomical darkness — midnight sun (Jun); white nights, twilight only (Apr, May, Jul, Aug). Part-faint months are dark on some nights only: dark from 10 Sep. ERA5 reanalysis, 2015–2024 monthly mean. Climatology, not a forecast — a regional ~25 km grid; local microclimates are not captured. Darkness & moon calendar → Best month, all spots →
Thresholds are averages from a dark site. Real visibility also needs clear skies, darkness and a cooperative moon — read every number as a chance, not a guarantee. The map is schematic: the oval is drawn around the geomagnetic pole and tuned to this place, so its edge reaches the marker at the Kp this page gives; the marker is approximate.