效果图:

源码如下:
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>jquery实现下雪功能</title>
<script src="http://libs.baidu.com/jquery/1.11.3/jquery.min.js"></script>
<style>
* {
margin: 0;
padding: 0;
}
body {
position: relative;
height: 1000px;
width: 100%;
overflow: hidden;
background-color: #666;
}
span {
display: block;
opacity: 0.7;
}
</style>
</head>
<body>
<script>
$(function () {
setInterval(function () {
const maxW = document.body.clientWidth,
maxH = document.body.clientHeight,
left = Math.random() * maxW,
bottom = left - (Math.random() - 0.5) * 0.2 * maxW, //保证落下的位置水平有变化,但不大
opacity = 0.7 + 0.3 * Math.random();
const speed = 30;
const size = 20 + 10 * Math.random(), //字体20-30
color = '#fff';
// num = Math.floor(Math.random() * 10) //产生0-9随机数,当然你们可以自己设置
const num = '*';
const style = 'position:absolute;top:0px;font-size:' + size + 'px;color:' + color + ';left:' + left + 'px;opacity:' + opacity;
const div = '<span class = "dd" style="' + style + '">' + num + '</span>';
$('body').append(div)
$('span').animate({
top: maxH,
left: bottom
}, 3000, function () {
$(this).remove() //这一步很关键,要把落下的去掉,不然会越积越多
});
}, 20) //20ms产生一个
})
</script>
</body>
</html>