In keeping with hovering between the autumn and the winter, I shall mention a paper I stumbled across a couple days ago. It isn't the simplest read, but its not too terrible, and it does something quite interesting. It applies environmental effects to 3D scenes. This isn't merely precipitation animation or a snowy texture being applied to the upper reaches of mountains. Instead, the paper describes a technique for placing logical bits of "environmental objects" into a scene in an integrated manner.
For example, it could add a scattering of autumn leaves atop the ground and other objects in the scene, in a properly-overlapping manner. It can add icicles, and piles of snow. Less naturally, bits of trash can be strewn about. All in all, it is a very interesting and powerful technique, because a basic scene could be designed, and then this technique could be applied. So the same basic scene could easily be set in different seasons. Pretty slick, if you ask me.
Details on the paper are below. The link to the PDF is available due to Professor Bedrich Benes of Purdue, one of the authors, who made it available from the servers of that fine institution.
Grosbellet, F., Peytavie, A., Guerin, E., Galin, E., Merillou, S., and Benes, B., (2016) Environmental Objects for Authoring Procedural Scenes. in Computer Graphics Forum 35(1), 296-308