I have seen clouds like that only once. I think I have the pictures, but I probably couldn't produce them on a dare. "My" clouds weren't as big or as well formed as that, but they were a sickly green color. Shortly after we noticed them, we had to take shelter because of the hail.
I think the clouds I linked to were the ones that produced softball sized hail.
As I said, if you are under clouds like that, seek shelter. (in her best motherly voice)
BTW, I posted that, went out for a quick ride, and got soaked in a spring shower. My weather luck is not good this year.
Give big space to the festive dog that make sport in the roadway. Avoid entanglement with your wheel spoke.
(Sign in Japan)
1978 Raleigh Gran Prix
2003 EZ Sport AX