HOUSTON (KTRK) --What caused this mysterious blue streak across Houston's morning sky? Meteorologist Travis Herzog says this is a thunderstorm cloud shadow illuminated by crepuscular rays.
These cloud shadows were formed by tropical showers below the horizon in the Gulf near Louisiana. They were visible all the way to New Braunfels and south Texas.
The crepuscular rays on the eastern horizon outlining the shadow over Houston fanned all the way across the sky to the western horizon where they appeared to converge again. When the rays are visible on the opposite side of the sky from the sun they are called anticrepuscular rays.
While the rays appear to converge at a point, this is an illusion caused by the curvature of the earth. The rays are actually parallel to each other.