The northern lights, also known as the aurora borealis, are tied to the 11 year sunspot cycle, so their frequency varies over time. Certain atmospheric conditions must be met to be able to see the northern lights when they occur, notes the Geophysical Institute at the University of Alaska Fairbanks.
The northern lights may be visible in Canadian towns such as Cochrane, Saskatoon and Edmonton during half of the year's dark, clear nights, although there may be only 10 of these total. Alaska, Iceland, northern Russia and Scandinavia also witness the northern lights relatively frequently, although Greenland and the eastern coast of Canada are usually too cloudy, notes the Geophysical Institute.
The northern lights can occur over parts of the continental United States, but conditions usually make them impossible to view. Overcast weather, light pollution and daylight all prevent the aurora borealis from being seen.
A similar phenomenon is sometimes visible in extreme southern locations. This aurora australis is visible in parts of Australia, South America, New Zealand and Antarctica.