While swimming at a friend's place, had a storm approach very quickly. It was so sunny out, just 10 minutes before this shot. Turns out, it was a very isolated storm cell that popped up unexpectedly to all. Only half the city experienced it.
In this pic, it almost looked like a twister was forming but it was just the clouds looking like that.
It was a 92° day but dropped 10 degrees in that 10 minute period from sunny to darkness and stormed for an hour. NO rain was predicted for the whole day.

Outdated Samsung camera phone

Cropped