.snow{
background-image:
        url(https://www.fibreopticlighting.com/image/snow/image-1.png),
           url(https://www.fibreopticlighting.com/image/snow/image-2.png),
           url(https://www.fibreopticlighting.com/image/snow/image-3.png);
animation: snow 30s linear infinite;
}

@keyframes snow {
    0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
    100% {background-position: 1000px 2000px, 1400px 1800px, 1800px 3000px}
  
}