Very Strange Sky In Las Vegas Today

Cathy and I were returning home this afternoon around 4:00 and we were by the Speedway on the far northeast side of Las Vegas.
We noticed the most unusual red sky to the west, by the mountains, so unusual, that we wanted to take pictures for the blog. The redness went north to south, the entire length of the valley.
We turned around to take the picture, about 15 seconds and the entire redness in the sky was gone. 15 seconds. Gone.
I have never seen anything like this before. Very strange and eerie.