The woods crashing through darkness, the booming hills, Winds stampeding the fields under the window Floundering black astride and blinding wet (2-4)
The wind is creating a lot of violent effects at this point of the poem—probably knocking off some branches and maybe felling some old trees—but it's not really that destructive. It's more that it's presenting the threat of violence.
[…] and wind wielded Blade-light, luminous black and emerald, Flexing like the lens of a mad eye. (6-8)
The wind wields "blade-light," but what does it really use it for? It's not actually going to annihilate the world or kill any humans (apparently). Again, it's just representing a threat. It could be a deadly if it wanted to be, and it moves like a mad eye because it isn't exactly rational.
Once I looked up— Through the brunt wind that dented the balls of my eyes The tent of the hills drummed and strained its guyrope, The fields quivering, the skyline a grimace,At any second to bang and vanish with a flap; (10-14)
The wind couldn't really blow the world away, but this exaggeration helps dramatize its power.
The wind flung a magpie away and a black- Back gull bent like an iron bar slowly. (15-16)
It's not that the wind, in this poem, really likes to beat up birds. It is just indifferent to the fates of humans and animals both.
The house Rang like some fine green goblet in the note That any second would shatter it. (16-18)
Again, the house won't actually shatter, but the sense that it somehow could is what matters. It's the pervasive sense of threat, yet again.
We watch the fire blazing, And feel the roots of the house move, but sit on, Seeing the window tremble to come in, Hearing the stones cry out under the horizons. (21-24)
Violence can kindle a strange kind of life, at the same time that it's destructive. It forces the inanimate world to cry out, apparently in protest.