The days are lengthening, making these weeks the best ones for viewing the aurora borealis.
"For reasons not fully understood by scientists, the weeks around the vernal equinox are prone to Northern Lights," the space agency said in this 2008 writeup of the aurora borealis, which goes by the name Northern Lights on Turtle Island. "Canadians walking their dogs after dinner, Scandinavians popping out to the sauna, Alaskan Huskies on the Iditarod trail—all they have to do is look up and behold, green curtains of light dancing across the night sky. Spring has arrived!"
In this video of dancing lights, NASA scientists describe both the mysterious phenomenon and attempts to study it.