I don't pay much attention to soil temp. I just go out once the snow is most melted, and start on sunny south facing slopes since these tend to thaw first. Its great if these happen to be sliding hills because stuff is near the top. Usually within a few days most places will be good for a few inches of digging.
Rodger, that's sort of what my yard in central Minn looks like too, but nearly a foot of melt in the last week. My goal is to be out hunting by April 1.