Sure, Hughes totally avoids rhyme in "Wind"—but he does let a few other sonic effects creep in. For instance, he uses assonance—matching up the long I sounds in "astride" and "blinding." Paired with the alliteration of the beginning BL- sounds of "black" and "blinding," this generates a dramatic, somewhat aggressive sound. The violence of the wind is magnified as a result: "Winds stampeding the fields under the window/ Floundering black astride and blinding wet" (3-4).
The poem also pairs alliteration with consonance. Check out the H, W, BL, and L sounds packed into the lines: "The hills had new places, and wind wielded/ Blade-light, luminous black and emerald" (6-7). In this case, the combination of "wind" and "wielded" provokes a sonic sense of the wind's combative swiftness. The W sounds push the air quickly out of our mouths, underscoring how the wind is quick to the fight and can attack and destroy at a moment's notice. The smoothness of the BL sound echoes reinforce how the wind can swing its "blade-light" around deftly.
Later, we see B-sound alliteration, L-sound consonance, and long-I assonance in the lines "The wind flung a magpie away and a black-/ Back gull bent like an iron bar slowly" (15-16). Again here, and throughout the poem, sonic choices echo from line to line. As a result, the poem sounds taut, tightly-knit, and the lines gain a certain energy from these sounds running into each other over and over. Even on a sound level, then, the wind is making its presence felt. Its violence is fueled by this sonic intensity.