Unusual light in the sky????

Hi everyone. Last Thursday afternoon I went out to the farm to haul corn as I was taking advantage of a warmer day. I was heading home about 5:30 pm. I was driving East and just about to turn North to go through Matawan. For those that have never heard of Matawan, It  is where Faribault, Freeborn and Waseca county meet. All at once the entire sky to the East and Northeast lit up! My first thought was lightning. But light lightning in late December with no thunderstorms??? Another thought was "heat lightning" that I have seen when it was really hot in the summer. Another thought was a "falling star" which I have seen a few times but it was cloudy at the time. Anyone have any ideas????