An example of how to write a big sun weather icon in pure CSS

<div class="container">
    <div class="sunny"></div>
</div>

body{
    background: rgba(73, 74, 95, 1);
}

.container{
    width: 170px;
    height: 170px;
    position: relative;
    margin: 250px auto;
}

.sunny{
    width: 20px;
    height: 140px;
    position: absolute;
    top: 20px;
    left: 90px;
    background: -webkit-linear-gradient(top, rgba(255,255,255,0) 0%, rgba(255,255,255,0.8) 50%, rgba(255,255,255,0) 100%);
    animation: sunny 15s linear infinite;
}

@keyframes sunny {
    0%{
        transform: rotate(0deg);
    }
    100%{
        transform: rotate(360deg);
    }
}

.sunny::before{
    content: '';
    width: 20px;
    height: 140px;
    position: absolute;
    bottom: 0;
    left: 0;
    background: -webkit-linear-gradient(top, rgba(255,255,255,0) 0%, rgba(255,255,255,0.8) 50%, rgba(255,255,255,0) 100%);
    transform: rotate(90deg)
}

.sunny::after{
    content: '';
    width: 80px;
    height: 80px;
    position: absolute;
    top: 30px;
    left: -30px;
    background: #ffee44;
    border-radius: 50%;
    box-shadow: rgba(255,255,0,0.2) 0 0 0 15px;
}