יִתֵּ֧ן יְהוָ֛ה אֶת־מְטַ֥ר אַרְצְךָ֖ אָבָ֣ק וְעָפָ֑ר מִן־הַשָּׁמַ֙יִם֙ יֵרֵ֣ד עָלֶ֔יךָ עַ֖ד הִשָּׁמְדָֽךְ׃
L’Éternel transformera la pluie de ton pays en poussière et en sable, qui descendront sur toi du haut du ciel jusqu’à ce que tu périsses.
Rashi
מטר ארצך אבק ועפר [GOD SHALL MAKE] THE RAIN OF THY LAND POWDER AND DUST, through “a wind that comes after the rain” as the Talmud says (Taanit 3b); rain will fall but not as much as is needed, so that there will not be sufficient of it to lay the dust; the wind will come and blow the dust about and cover the leaves of the vegetation which are still wet from the water and it will adhere to them and so become mud which will afterwards become dry, and they will rot (Taanit 3b).
Chizkuni
אבק ועפר, “powder and dust;” the strong winds which normally bring rain from the sky, will instead be sandstorms originating in the tops of the mountains so strong that they turn the trees’ roots upside down.
Ibn Ezra
powder and dust due to the great dehydration [: 22] and the powerful winds.