Polar night

The polar night is when it stays dark outside for more than twenty four hours. This occurs only inside the polar circles (the northernmost and southernmost areas on Earth). A lot of times It will be a polar night for the winter and the opposite happens in the summer.

 References 

 Other websites 

 The polar night and polar darkness
 Many years' of webcam pictures from Tromsø, Norway.  These clearly show the progression into and away from winter at a latitude within the Arctic Circle.

Category:Geography
Category:Astronomical phenomena