$(function() {

  $.fn.snow({ duration: 5 * 60 * 1000 }); // 5 min

});

​

/** 

 * jquery.snow 1.1

 */

​

(function($) {

  $.fn.snow = function(options) {  

    var $flake = $("<div/>", { 

        "class": "flake",

        css: {"position": "absolute", "top": "-50px"},

        html: "❄"

      }),

      documentHeight = $(document).height(),

      documentWidth = $(document).width(),

      defaults = {

        minSize: 10,

        maxSize: 20,

        newOn: 500,

        flakeColor: "#FFFFFF",

        duration: null

      },

      options = $.extend({}, defaults, options),

      passed = 0,

      interval;       

    interval = setInterval(function() {

      var startPositionLeft = Math.random() * documentWidth - 100,

        startOpacity = 0.5 + Math.random(),

        sizeFlake = options.minSize + Math.random() * options.maxSize,

        endPositionTop = documentHeight - 40,

        endPositionLeft = startPositionLeft - 100 + Math.random() * 200,

        durationFall = documentHeight * 10 + Math.random() * 5000;

      $flake

        .clone()

        .appendTo("body")

        .css({

          left: startPositionLeft,

          opacity: startOpacity,

          fontSize: sizeFlake,

          color: options.flakeColor

        })

        .animate({

          top: endPositionTop,

          left: endPositionLeft,

          opacity: 0.2

        }, durationFall, "linear", function() {

          $(this).remove();

        });

        if (options.duration !== null) {

          passed += options.newOn;

          if (passed >= options.duration) clearInterval(interval);

        }

      }, options.newOn);  

  };  

})(jQuery);