I was driving east on 635 when the entire eastern sky towards Dallas lit up teal green , quite brightly. This was easy to notice since it was early morning and the sun was not yet up. I checked the weather and it was supposed to be cloudy but no lightning was in the forecast. I should mention the light was shrouded by the clouds ,so I didn't get to see what was emitting the light. I just know it was brighter and greener than any light I had ever seen . This lasted only a second but I felt compelled to report it as I've seen no trace of any news story here locally that reports an explanation.