What is the meaning of Hilda Doolittle's poem "Heat"?

It's not necessarily about such a precise subject, since the poem does not give you precise clues. So you have to accept that imprecision. I see it more as an opposition of two forces, heat and wind, one that prevents life from being fruitful, and the other that could oppose its own violence to the heat. "Heat" prevents life and stifles. It is a static force, while the wind is in motion.