.snow {
  /*雪の色*/
  color: snow;
  /*雪の大きさ*/
  font-size: 10px;
  /*初期位置*/
  position: fixed;
  top: -5%;
  /*雪を適当な幅で降らせる*/
  text-shadow:
  5vw   -100px 2px,
  10vw  -400px 3px,
  20vw  -500px 4px,
  30vw  -580px 1px,
  39vw  -250px 2px,
  42vw  -340px 5px,
  56vw  -150px 2px,
  63vw  -180px 0,
  78vw  -220px 4px,
  86vw  -320px 9px,
  94vw  -170px 7px;
  /*雪アニメーション1*/
  animation: roll 5s linear infinite;
}
  /*2つめの雪アニメーション*/
.snow2nd{animation: anim 8s linear infinite;}

@keyframes roll {
    0% {transform:rotate(0deg);}
   90% {opacity:1;}
   100% {transform:rotate(20deg);top:100%;opacity:0;}
}
@keyframes anim {
  100% {color:transparent;top:150%;}
}