Charles Ellicott Commentary Jeremiah 4:11

"At that time shall it be said to this people and to Jerusalem, A hot wind from the bare heights in the wilderness toward the daughter of my people, not to winnow, nor to cleanse;" — Jeremiah 4:11 (ASV)

At that time. —that is, when the lion and destroyer of Jeremiah 4:7 should begin his work of destruction.

A dry wind. —Literally, a clear wind, the simoom, the scorching blast from the desert, coming clear and without clouds. Other winds might be utilized for the threshing-floor, but this made all such work impossible, and was simply devastating, and was therefore a fit symbol of the terrible invader.