Valdood sent me this picture: "It's a weather-changing coming in from the Northsea. We can see this kind of clouds after a period of very warm weather that comes to an end when a depression is rolling in from sea. We call it a "rolwolk" (roll cloud) and there's a lot of rain and thunder in it."

It is certainly a reminder of the massive power that mother nature can muster, and a very impressive sight. Valdood gets 5 Euros to play for!