Low Saxon (“Low German”) Swark (pronounced [svaːk], rhyming with “dark” said with an Australian accent) is an ominously dark bank of clouds seen at the horizon.

The most impressive, unforgettable cases of Swark (as well as thunderstorms) I ever witnessed were in North Central China in July, while traveling by train westward to Xinjiang (Eastern Turkestan), the part of Central Asia that is governed by China.

Swark has a Dutch relative: zwerk.