Is there a good method for dynamically drawing clouds with HTML5 canvas and javascript without using images?

I am trying to create a background for my website that uses canvases to draw stuff, get the data URL of it and set it as the background-image property of an element. The method works, but I can't find a good way to draw a cloud on the canvas. Other simpler things like the sun and stars are easy to do without images, and I would prefer to keep the entire script image-less. Drawing a multitude of circles around a point can slightly do it, but I would prefer a more realistic way to do it. Thanks in advance.