SEATTLE - The Northern Lights are caused when the sun gives off electrically-charged particles from solar flares. The Earth's magnetic poles act like, well, a magnet to draw those particles to the polar regions. When the particles interact with the atmosphere, the give off the beautiful ribbons of purple, blue, red and green.
They're most common around the Arctic Circle, but during particularly strong solar flares, they can be seen as far south as Arizona.
Solar flares are supposed to increase over the next few months, so keep an eye to the northern sky on clear nights and maybe you'll catch them.
For More Information About Northern Lights:
SpaceWeather.com -- good for letting you know when a big Northern Lights Display is coming.
Northern Lights Forecast -- www.gi.alaska.edu
Northern Lights Right Now -- www.sec.noaa.gov
Viewing Tips -- www.sec.noaa.gov