When are the Aurora Borealis most likely to appear in Finnish Lapland?

The particles causing the Northern Lights come from the sun, from which they are catapulted out into space at speeds of up to 1000 km a second on the so-called solar winds. The Northern Lights typically form at a height of 100 km as a result of charged particles (electrons and protons) accelerating in the Earth's magnetic field and colliding with air molecules. These give up part of their surplus energy in the form of light. The phenomenon is rather similar to the formation of an image in a television tube, or to the emission of light by a neon lamp. The usual greenish-yellow, and occasionally reddish, appearance of the aurora is produced by the oxygen in the atmosphere, whereas the blue and violet light is due to nitrogen.

The Finnish name for the lights (revontulet) comes from a Sami, or Lapp, legend whereby the tail of a fox running along snow-covered fells strikes the snow drifts, sending a trail of sparks into the sky. Revontulet literally means "foxfire".

The systematic observation of the Northern Lights began in Finland in the mid -1700’s. From the 1970’s the Finnish Meteorological Institute has operated auroral cameras at several stations allowing them to compile extensive statistics, images and monitor seasonal variations.

Today, the FMI maintains a modern digital all-sky camera system that takes the auroral pictures without film directly to the memory of a computer. At the moment there are five cameras in operation. The pictures are transmitted, principally in real-time, through Internet to be seen everywhere. Due to light nights in Lapland during spring and summer, the auroral cameras have been switched off. The photographing begins again in autumn.

Where and when are the Northern Lights most seen?
Statistics reveal that the most Northern Lights are observed in the Kilpisjärvi region of Lapland. With a clear sky during the dark period of the year on average the auroras is seen there on three nights out of four.  The 100 % (every night) level is only attained in northern Norway, along the shore of the Arctic Ocean. Further north still their occurrence again decreases. As one travels south, the incidence diminishes so that in the Sodankylä region the Northern Lights are seen every second night, and in the Oulu-Kuusamo area every fourth night.  On cloudy nights, of course, it is not possible to see them at all.

 
At 9 pm in the evening, Finnish time, the average probability of occurrence in Lapland exceeds 50 %. It reaches a peak at approx. 11.30 pm, when there is a magnetic midnight and the disturbances in the Earth's magnetic field that the lights depend on are at a maximum. After midnight the incidence of the lights dwindles, so that by 4 am to 5 am the probability of occurrence falls below 50 %.
In North-Finland, north of the Arctic Circle, the best season for seeing auroras is December - January. During the summer, the nights are too bright for observing auroras.

For the best locations to experience the Northern Lights this winter click here.