Thunderstorm rapidly spreading around the area.

Don't ever recall one with as many lightning strikes. Could see the "sparks" over a broad front as it approached, and the rumbling was continuous for over half an hour. To some extent the above looked like a cloud formation you might see in a storm chaser time lapse video. Taken with a fisheye lens, so a wide scene is captured, that looks further away than reality. The cloud front had multiple layers spreading far off to the right of the frame. As I was lifting the camera to my eye, there was a substantial lightning strike from near the front of the above formation, 45 degrees back the way, to the heavy rain zone, and the ground.

Didn't hang about. Reached home as the rain commenced.