Big solar flares caused a space weather storm a few days ago. The Kp index got up to 8; if it had gotten to 9, aurora would have been visible from Boulder (40 degrees north latitude). As it was, people saw great displays as far south as Ohio.

Spaceweather.com is a good clearinghouse for such things; they even have a phone service that will call you in the middle of the night if something is worth getting up for. But for the real data, nothing beats the Space Environment Center at NOAA.