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HTML 

              
                <div id="snowfall">
  <div class="snow"></div>
  <div class="snow1"></div>
  <div class="snow2"></div>
</div>
!

CSS 

              
                body {
  height: 100vh;
  background-image: linear-gradient(0deg, #fff 0%, #73bfdc 100%);
}

#snowfall {
  position: absolute;
  width: 100%;
  height: 100px;
}

.snow {
  position: absolute;
  border-radius:50%;
  filter: blur(1px);
  background-color: #fff;
  width: 10px;
  height: 10px;
  top:-1000px;
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
  animation: snowfall 7s linear infinite;
}

.snow:before {
  content:"";
  width:7px;
  height:7px;
  position: absolute;
  background-color: #fff;
  left: 200px;
  top:-150px;
  border-radius:50%;
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
  
}

.snow:after {
  content:"";
  width:5px;
  height:5px;
  position: absolute;
  background-color: #fff;
  left: 300px;
  top:-250px;
  border-radius:50%;
  filter: blur(1px);
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
}
.snow1 {
  position: absolute;
  border-radius:50%;
  filter: blur(2px);
  background-color: #fff;
  width: 9px;
  height: 9px;
  top:-850px;
  left:123px;
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
  animation-delay:-3s;
  animation: snowfall 9s linear infinite;
}

.snow1:before {
  content:"";
  width:7px;
  height:7px;
  position: absolute;
  background-color: #fff;
  left: 200px;
  top:-350px;
  border-radius:50%;
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
  
}

.snow1:after {
  content:"";
  width:5px;
  height:5px;
  position: absolute;
  background-color: #fff;
  left: 300px;
  top:-450px;
  border-radius:50%;
  filter: blur(1px);
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
}

.snow2 {
  position: absolute;
  border-radius:50%;
  filter: blur(1.5px);
  background-color: #fff;
  width: 9px;
  height: 9px;
  top:-900px;
  left:-50px;
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
  animation-delay:-4s;
  animation: snowfall 14s linear infinite;
}

.snow2:before {
  content:"";
  width:7px;
  height:7px;
  position: absolute;
  background-color: #fff;
  left: 200px;
  top:-550px;
  border-radius:50%;
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
  
}

.snow2:after {
  content:"";
  width:5px;
  height:5px;
  position: absolute;
  background-color: #fff;
  left: 300px;
  top:-650px;
  border-radius:50%;
  filter: blur(1px);
  box-shadow: 20px 20px 1px #fff, 60px 40px 1px #fff, 160px 135px 1px #fff, 260px 240px 1px #fff, 360px 340px 1px #fff, 460px 440px 1px #fff, 560px 340px 1px #fff, 660px 240px 1px #fff, 760px 140px 1px #fff, 260px 640px 1px #fff, 160px 340px 1px #fff, 260px 440px 1px #fff, 760px 140px 1px #fff,860px 40px 1px #fff, 760px 140px 1px #fff, 1260px 120px 1px #fff, 1460px 10px 1px #fff,1560px 30px 1px #fff, 1590px 124px 1px #fff, 1680px 415px 1px #fff, 1720px 335px 1px #fff,1000px 212px 1px #fff, 990px 311px 1px #fff, 888px 122px 1px #fff, 765px 10px 1px #fff, 635px 15px 1px #fff, 554px 111px 1px #fff, 455px 222px 1px #fff, 125px 105px 1px #fff, 275px 96px 1px #fff, 245px 40px 1px #fff, 230px 70px 1px #fff, 285px 17px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 360px 340px 1px #fff, 430px 210px 1px #fff, 523px 23px 1px #fff, 1650px 335px 1px #fff, 1777px 123px 1px #fff, 1800px 222px 1px #fff, 1360px 140px 1px #fff;
}

@keyframes snowfall {
    100% {transform: translateY(1500px);}
}
!

JS
!
999px

Console