The light pollution is a big factor that affects the visibility of the Northern Lights. That is the reason why companies who operate the Northern Lights tours drive outside the city in order to get higher chances of seeing them. 2. Moon: A natural source of light which cannot be turned off, and we cannot get away from it. Sometimes when the Moon is very bright, it makes it harder to see the Northern Lights. However, every night is different and there is not a rule. If we are lucky, we will get some clouds that will cover it for a while so we can enjoy of a good aurora show.3. The clouds: Iceland is a country with a lot of micro systems. Saying this, the weather is really hard to predict. If you do not believe me, check en.vedur.is on a certain date/time, and compare it with the actual weather. Maybe 80% of the times it will be inaccurate (sorry guys).4. Solar activity:Giving that the Northern Lights come from the solar interaction with the Earth's atmosphere, this will affect its visibility.