The I-10 is like most interstates - flat, straight and boring, but gets you places fast. Florida's panhandle, being flat, straight and boring itself, multiplies those qualities in the freeway. Simply put, driving down the I-10 feels much like being stationary. Blue sky above, green jungle on the sides, and asphalt below, the only way to tell that you are going anywhere is the continuous reduction of the GPS's "time left" counter.
When something like this pops up in the sky, it's an event. It just hovered there, right above the freeway, like der Wolkenkönig. Unfortunately, stopping on the freeway is not recommended, but at least I could exit and get a shot of it. I was hit by its downpour a couple of minutes later.