After days of sweltering heat, Peter Beelen (Member 40,643) was happy to see the grey layer of Stratocumulus gather over Eindhoven, Netherlands, accompanied by rapidly cooling temperatures.

The well-defined and chaotic undulations in the cloud’s base are features known as asperitas, meaning ‘roughness’, which resemble the surface of a choppy sea seen from below.

Choppy or not, the sea would have been refreshing for a dip after such hot weather, but Eindhoven is far inland. Instead, the cooling showers that Peter tells us followed 15 minutes later were a welcome alternative.