Some nights it seems like there are three main sunsets: 1. When the sun sets behind the horizon; 2. When the first round of cloud glow kicks off after the sun sets behind the horizon; and, 3. Once in awhile a second round of glow comes to the clouds just as blue hour is kicking off.
Last night was just such a night here in Fort Fun, yay!
Image Notes: Manually blended two exposures for foreground and sky. Shooting blue hour can result in some fantastic results, but experiment with exposure. For e.g. this image is a tad brighter than the scene was in reality.