Not an expert on weather related pond disasters. (The watersheds for my ponds are very small.)
However, I don't believe a few days of cold AIR temperatures can generally damage a fish population. It certainly can change fish behavior.
The stories I have read on Pond Boss concerning spring fish kills have almost always referred to warming ponds that were hit with a very cold 1.5"+ rain in the water shed. That can be a shocking change to a fish population.
