According to Spaceweather.com: “The first of two CMEs expected to hit Earth’s magnetic field on Sept. 12th arrived on schedule. Although the geomagnetic storm it provoked was technically only minor (G1-class), Northern Lights were observed as far south as Arizona.”
Spaceweather further reports: “A second and potentially more powerful CME is still en route. Geomagnetic storming could become strong (G3-class) during the late hours of Sept. 12th and Sept 13th after the second CME arrives. NOAA forecasters estimate a 45% chance that geomagnetic storming will reach mid-latitudes. Sky watchers everywhere should remain alert for auroras.”
For more information see http://spaceweather.com/. If you happen to be in an area that has clear skies late on September 12, you might want to take a look!