At that time - See Jeremiah 4:7. Though the revelation of the certainty of Judah’s ruin wrings from Jeremiah a cry of despair, yet it is but for a moment; he immediately returns to the delivery of God’s message.
A dry wind - literally, A clear wind. The Samum is probably meant, a dry parching east wind blowing from the Arabian desert, before which vegetation withers, and human life becomes intolerable.
Not to fan ... - The Syrian farmers make great use of the wind for separating the chaff from the grain: but when the Samum blows labor becomes impossible. It is not for use, but for destruction.