It is possible to understand low temperature spin waves in classical spin systems in terms of a phenomenological ’’fixed‐length’’ hydrodynamic theory. The particular hydrodynamic theory appropriate for magnets with an underlyingXYsymmetry is exactly soluble, and seems to give a good description of equilibrium order parameter dynamics in one, two, and three dimensions. Here, we exploit this exact solubility to study spin wave dynamics far from equilibrium. Spin waves dominate the nonequilibrium equal‐time correlation functions. In two dimensions, for example, two point equal‐time correlations decay from a state of complete alignment by propagating a cusp‐like singularity from short distances toward large. The cusp travels at twice the spin wave velocity, and leads tok‐space oscillations in the Fourier‐transformed spectrum, ? (k,t). If these oscillations could be detected, they would show up as a time‐dependent bull’s‐eye pattern surrounding Bragg peaks in a neutron diffraction experiment.