Hypersomnia is more common in October, reports Shape.

Autumn and Your Energy Levels
Ever heard of hypersomnia? It’s the technical term for sleeping too much (the opposite of insomnia) and it tends to crop up during the fall months. In fact, most people sleep more in October—roughly 2.7 hours more per day—than during any other month of the year, shows a study from Harvard Medical School. A little extra shuteye may sound like a good thing. But the same Harvard study found the quality and deepness of your sleep also suffer, and people report feeling groggier during the day. Why? Thanks to shorter (and often rainier) days, your eyes aren’t exposed to as much bright sunlight as they enjoyed during the summer, the authors say.