Thanks, Tom, you said it better than I could!

In addition, any precipitation in April will be in the form of snow. At that time of year, it might be wet, soggy snow, or it might be a howling blizzard. "Spring" in Wyoming, even at lower altitudes, generally doesn't happen until mid to late May. In Yellowstone, it can snow any month of the year.
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey