Location: Scottsdale, AZ
I recently learned about a weather phenomenon known as noctilucent clouds (which no doubt everybody reading this already knows are extremely high-altitude, edge-of-space, swirly-type clouds that form at latitudes between 50°N and 65°N.) Although they are usually not visible as far south as where I live (unless they were created by a missile launched early in the morning at the White Sands test range in nearby New Mexico and are an amazing site to behold), I believe I have seen some (or something similar) on a few of my recent early morning outings.
So when I found myself awake at 3:00 am several mornings this week, I took my camera and my dog for a long walk and photographed until nearly 5:00 am, hoping (unsuccessfully, alas) to see noctilucent clouds high in the sky. By this time, the sunrise is fast approaching and the sky quickly turns from black to a very vibrant, almost electric blue for a few, brief minutes before Night hands-off control of the sky's color to Day, at which point it will change to sky blue, the color after which it was named.
This same effect occurs after sunset, except in reverse (i.e., the sky grows darker and blacker, not lighter), and photographers refer to it as "The Blue Hour," because it lasts roughly that long before the blue finally fades into black (which is actually how the naked eye perceives the sky the whole time.)
In reality, there are two Blue Hours each day and the photo I'm posting today was taken during the first of them! And before you ask, Yes, for a few minutes around 4:30 am on Thursday morning, the sky really was the vibrant blue I captured in this photo. 8^)