dojo/css/snow.css

.snow{
    position:fixed;
    pointer-events:none;
    top:0;
    left:0;
    right:0;
    bottom:0;
    height:100vh;
    background: none;
    background-image: url('/img/snow/s1.png'), url('/img/snow/s2.png'), url('/img/snow/s3.png');
    z-index:100;
    -webkit-animation: snow 10s linear infinite;
    -moz-animation: snow 10s linear infinite;
    -ms-animation: snow 10s linear infinite;
    animation: snow 10s linear infinite;
  }
  @keyframes snow {
    0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
    50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
    100% {background-position: 500px 1000px, 200px 400px, -100px 300px;}
  }
  @-moz-keyframes snow {
    0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
    50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
    100% {background-position: 400px 1000px, 200px 400px, 100px 300px;}
  }
  @-webkit-keyframes snow {
    0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
    50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
    100% {background-position: 500px 1000px, 200px 400px, -100px 300px;}
  }
  @-ms-keyframes snow {
    0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
    50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
    100% {background-position: 500px 1000px, 200px 400px, -100px 300px;}
  }