SEATTLE - It really can't be too cold to snow, as snow can occur even in temperatures below zero (although it's rare). But the colder it is, the more difficult it is to make it snow.
That's because colder air simply can not hold as much moisture as warmer air. So in that sense, it's "easier" for it to snow at 30 degrees than at 10 degrees, because there can be more moisture to work with in the air to make it snow.
But as long as you have a way for air to lift, such as air going up a mountain or heating at the surface, or a good source of moisture, like air moving over a large body of water, you can get snow at very low temperatures. For example, it snows in Antarctica despite temperatures routinely below zero.