Shortly before sunset on Jan. 7, 2022, in the western sky in the Chicago area there was a layer of clouds that looked like it had a hole punched through it, with wispy clouds falling through. What causes that?
—Leanne C. L.
The photograph that you provided shows a hole in a deck of altocumulus clouds (mid-level clouds occurring at a height of about 7,000 to 15,000 feet). I estimate the height of this particular altocumulus layer was about 8,000 feet. Jet aircraft flying through such clouds cause the holes. The altocumulus were composed of super-cooled water droplets that, disturbed by the aircraft, froze, stuck together and fell out, creating the hole that you observed. As the water droplets freeze and fall, they create a hole in the cloud deck.