Just yesterday, I told this story to a bunch of people: My godfather invited me to go deer hunting with his wife's family in Unity, ME when I was 15yrs old. I was excited to do it and drove the family car to meet him there, then transferred to another vehicle and met some other guys at a hunting spot along a gravel road near an intersection and placed me there to cover it. There was a friend of theirs who was acting like a guide/trail-guy and he went into the woods to find, and hopefully push deer to the others positioned around the area, including me.
Well it started snowing, and the flakes were quarter-sized! About a half-hour, a nice buck came out and stood on other edge of the road I was guarding, about a hundred yards away! I was excited and brought my iron-sighted Savage 110, 30-06 up to shoot, but a large flake landed on my REAR sight. I brushed it off with my gloved hand and raised the rifle again. Taking a bead on the deer, another, larger flake landed on the FRONT sight. I was getting quite frustrated at that point, but raised the rifle again and aimed, fully expecting another flake on the sights, but it didn't happened yet, so quickly placed the sights on the deer and fired...probably too quickly, because at the shot, the buck jumped and ran back the way it came. I walked ahead and found the spot where it came to the road, but no sign of a hit. The "guide" and my cousin came out too, and the guide went to follow the tracks, but never saw the deer.
I was very upset at missing the nice buck, but knew that conditions played a huge role in the miss. I can still see the situation in my mind. Today, I would have had a scope and probably would have killed the deer. Experience is a very good teacher.