The Lord shall make the rain of thy land powder and dust
That is, instead of showers of rain in their season, to water, refresh, and enrich the earth, and make it fruitful; and for want of them, and through the heat of the sun, being dried and parched, and its clods crumbled into dust, this should be raised up into the air by the force of winds, and let down again in showers of dust; whereby the few herbs, plants, or green trees on it would be utterly destroyed: and so the Targum of Jonathan interprets it of the Lord's sending a wind that should raise the dust and earth upon the herbs of their fields. Such ploughing winds, that cast up the earth and sand, and dust, into the air, whereby men and cattle are sometimes covered, are frequent in the eastern countries; of which (See Gill on Jonah 4:8);
from heaven shall it come down upon thee until thou be destroyed;
that is, from the air, up to which the dust is carried by the wind, and then let fall in vast quantities, like showers, which are very destructive.
The Brenton translation of the Septuagint is in the public domain.