Tromsø, a city situated at 70° north in Norway, is in the middle of the auroral oval, the area with the highest probability of seeing the Northern Lights. The best period to experience the Northern Lights is from early September to early April. During large solar explosions and flares, large quantities of charged particles are thrown from the sun and into deep space. When the particles meet the Earth’s magnetic shield, they are pulled in an oval around the magnetic North Pole where they interact with upper parts of the atmosphere. The Northern Lights are at least 80 km above the Earth’s surface, much higher than clouds. Consequently, a clear sky creates the best backdrop for viewing them.