Photo: Clouds (explained)

Puget Sound from Richmond Beach
Photo by Lee Lageschulte

WeatherWatcher Carl Dinse explains:

These are the classic Cumulonimbus clouds that form when we have cold air aloft (that means the upper atmosphere was much colder than normal) with a ground being warmed up by the sun.

When the clouds get big enough and tall enough they produce heavy rain, hail, and lightning (thunder).

The clouds in this picture were the start to the formation of an active disorganized convergence zone event Tuesday evening that started about 6pm and ended around 8pm. Most of it stayed just north of the county line.

There were other heavy showers across the region but this was by far the most consistent and formed structure of the evening.