You can continue to wear your longer length shorts, and short skirts into fall & winter by adding longer boots, and tights.
Wear over the knee boots, and make sure they are under your longer shorts with no leg showing if you aren’t wearing tights. If you are wearing tights, make sure the tights are the same color as the boots, or your top. If you are going to use the tights as a featured accessory then you can use a patterned or textured tight for that purpose.
Here is an example of wearing a faux leather skirt with tights and boots that are the same color. It will elongate the legs, and make any outfit look styled.