.clouds {   position: relative;   overflow: hidden;   height: 400px; } .initialCloud {   position: absolute;   left: 100%;   top: 150px;   animation: moveFirst 5s linear .2s;   animation-iteration-count: 1;   width: 150px; } .firstCloud {   position: absolute;   left: -30%;   top: 150px;   animation: move 5s linear 5s infinite;   width: 150px; } .secondCloud {   position: absolute;   left: -30%;   top: 200px;   animation: move 8s linear 0s infinite;   width: 150px; } .thirdCloud {   top: 250px;   left: -30%;   position: absolute;   animation: move 11s linear 1s infinite;   width: 150px; } @-webkit-keyframes move {   from {     left: -30%;   }   to {     left: 100%;   } } @-webkit-keyframes moveFirst {   from {     left: 50%;   }   to {     left: 100%;   } }
<div class="clouds">
  <div class="initialCloud">
    <svg id="svgCloud" data-name="clouder" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 348 164"><defs><style>.cloud1Fill{fill:#d1dbd9;}</style></defs><title>Untitled-5</title><path class="cloud1Fill" d="M348,107.5a54.5,54.5,0,0,1-94.87,36.61,77.55,77.55,0,0,1-81.57-1.43A73,73,0,0,1,71,145.07,42.48,42.48,0,1,1,49.61,71.59,73,73,0,0,1,154.85,26.84,77.51,77.51,0,0,1,287.16,53.37,53,53,0,0,1,293.5,53,54.5,54.5,0,0,1,348,107.5Z"/></svg>
  </div>
  <div class="firstCloud">
    <svg id="svgCloud" data-name="clouder" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 348 164"><defs><style>.cloud1Fill{fill:#d1dbd9;}</style></defs><title>Untitled-5</title><path class="cloud1Fill" d="M348,107.5a54.5,54.5,0,0,1-94.87,36.61,77.55,77.55,0,0,1-81.57-1.43A73,73,0,0,1,71,145.07,42.48,42.48,0,1,1,49.61,71.59,73,73,0,0,1,154.85,26.84,77.51,77.51,0,0,1,287.16,53.37,53,53,0,0,1,293.5,53,54.5,54.5,0,0,1,348,107.5Z"/></svg>
  </div>
  <div class="secondCloud">
    <svg id="svgCloud2" data-name="cloud2" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 291 124"><defs><style>.cloud1Fill{fill:#d3dddb;}.cloud2Fill{fill:#fff;}</style></defs><title>Untitled-4</title><path class="cloud1Fill" d="M2.29,123.5A41,41,0,0,1,58.37,74.12l.32.14.24-.25A45.72,45.72,0,0,1,91.5,60.5q1.14,0,2.25.06l.43,0,.09-.41a76,76,0,0,1,148.46,0l.09.4h.41l1.27,0a46.06,46.06,0,0,1,46,46,45.53,45.53,0,0,1-3.26,17Z"/><path class="cloud2Fill" d="M168.5,1a75.53,75.53,0,0,1,73.74,59.23l.18.81.82,0,1.26,0a45.49,45.49,0,0,1,42.4,62H2.66A40.53,40.53,0,0,1,58.17,74.57l.63.29.49-.49A45.2,45.2,0,0,1,91.5,61c.75,0,1.5,0,2.23.06l.85,0,.18-.83A75.51,75.51,0,0,1,168.5,1m0-1A76.52,76.52,0,0,0,93.78,60.06Q92.66,60,91.5,60A46.35,46.35,0,0,0,58.58,73.66,41.52,41.52,0,0,0,1.92,124H287.58A46.5,46.5,0,0,0,244.5,60l-1.28,0A76.53,76.53,0,0,0,168.5,0Z"/></svg>
  </div>
  <div class="thirdCloud">
    <svg id="svgClouds3" data-name="clouds2" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 329 139"><defs><style>.cloud2Fill{fill:#d1dbd9;}</style></defs><title>Untitled-6</title><path class="cloud2Fill" d="M329,125a40.09,40.09,0,0,1-2.52,14H14.9A61.28,61.28,0,0,1,0,99C0,64.21,29.33,36,65.5,36a67.34,67.34,0,0,1,30,7A86,86,0,0,1,236.42,31.37,55.53,55.53,0,0,1,311,83.5a56.67,56.67,0,0,1-.55,7.75A39.93,39.93,0,0,1,329,125Z"/></svg>
  </div>
</div>

https://stackoverflow.com/questions/47754999/css-animation-absolute-position-go-off-screen-to-right-and-come-back-from-left