The Northern Lights, or aurora borealis, will be visible across areas like Seattle, Des Moines [Iowa], Chicago, Cleveland, Boston, and Halifax [Nova Scotia] on Wednesday. That night the KP-index, which measures global auroral activity ranges from 0 to 9, will be at Kp-5. Anything above a Kp-5 rating means a geomagnetic storm will occur. On Thursday, the aurora will intensify as the KP-index increases, making the colorful lights more visible, according to The Geophysical Institute at the University of Alaska at Fairbank.