In most parts of the world, the northern lights, or aurora borealis, are visible between late fall until early spring. In extremely northern areas, the lights may be visible from early fall until late spring.
The darker the night sky, the more visible the northern lights. This is why the northern lights are best viewed in regions that have extended periods of night during the winter, such as Sweden, Finland, Norway and parts of Alaska. The northern lights are caused by a disruption in the Earth's magnetic fields caused by solar winds that create particle trails. The most common colors for the northern lights are red, green and purple.
The northern lights are a regular occurrence in the extreme north, but it is impossible to predict exactly when and for how long they will be visible. Unfortunately, another difficulty in viewing the northern lights is that they tend to be the most active during some of the coldest and harshest parts of winter in the area in which they are visible. Planning a vacation specifically to view the aurora borealis can be a bit tricky. Although many who have viewed the aurora borealis also report a fuzzy or crackling noise, attempts to scientifically document such noises have failed.