CSS only snow animation. All credits goes to https://carloseo.com/let-it-snow-css-animation/

snow.css

.snow{
   background-image:
           url(https://user-images.githubusercontent.com/2805640/34124910-ec43e9a2-e434-11e7-85e5-0caebbe8ae94.png), 
           url(https://user-images.githubusercontent.com/2805640/34124916-f2bd028c-e434-11e7-8cf4-71d50265798f.png), 
           url(https://user-images.githubusercontent.com/2805640/34124918-f435eb42-e434-11e7-85c6-576e94b90377.png);
   width: 100%;
   height:100%;
   position: absoulute;
   top: 0;
   left: 0;
   z-index:1;
   animation: snow 20s linear infinite;
}
@keyframes snow {
    from {background-position: 0px 0px, 0px 0px, 0px 0px;}
    to {background-position: 500px 1000px, 200px 400px, -100px 300px;}
}

snow.html

<div class="snow"> </div>

images :